diff --git a/frameworks/ans/src/notification_helper.cpp b/frameworks/ans/src/notification_helper.cpp
index 0277e776700f5472022092366e5160c1d8fc2ba2..34dce1c8468455a29cafd62e9ad9d8e274401559 100644
--- a/frameworks/ans/src/notification_helper.cpp
+++ b/frameworks/ans/src/notification_helper.cpp
@@ -74,14 +74,14 @@ ErrCode NotificationHelper::SetNotificationSlotFlagsAsBundle(const NotificationB
 }
 
 ErrCode NotificationHelper::PublishNotification(const NotificationRequest &request,
-    std::string instanceKey)
+    const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->PublishNotification(
         request, instanceKey);
 }
 
 ErrCode NotificationHelper::PublishNotification(const std::string &label,
-    const NotificationRequest &request, std::string instanceKey)
+    const NotificationRequest &request, const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->PublishNotification(
         label, request, instanceKey);
@@ -92,20 +92,20 @@ ErrCode NotificationHelper::PublishNotificationForIndirectProxy(const Notificati
     return DelayedSingleton<AnsNotification>::GetInstance()->PublishNotificationForIndirectProxy(request);
 }
 
-ErrCode NotificationHelper::CancelNotification(int32_t notificationId, std::string instanceKey)
+ErrCode NotificationHelper::CancelNotification(int32_t notificationId, const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->CancelNotification(
         notificationId, instanceKey);
 }
 
 ErrCode NotificationHelper::CancelNotification(const std::string &label, int32_t notificationId,
-    std::string instanceKey)
+    const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->CancelNotification(
         label, notificationId, instanceKey);
 }
 
-ErrCode NotificationHelper::CancelAllNotifications(std::string instanceKey)
+ErrCode NotificationHelper::CancelAllNotifications(const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->CancelAllNotifications(instanceKey);
 }
@@ -130,7 +130,7 @@ ErrCode NotificationHelper::GetActiveNotificationNums(uint64_t &num)
 }
 
 ErrCode NotificationHelper::GetActiveNotifications(
-    std::vector<sptr<NotificationRequest>> &request, std::string instanceKey)
+    std::vector<sptr<NotificationRequest>> &request, const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->GetActiveNotifications(
         request, instanceKey);
@@ -382,7 +382,7 @@ ErrCode NotificationHelper::GetShowBadgeEnabled(bool &enabled)
     return DelayedSingleton<AnsNotification>::GetInstance()->GetShowBadgeEnabled(enabled);
 }
 
-ErrCode NotificationHelper::CancelGroup(const std::string &groupName, std::string instanceKey)
+ErrCode NotificationHelper::CancelGroup(const std::string &groupName, const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->CancelGroup(
         groupName, instanceKey);
@@ -527,7 +527,7 @@ ErrCode NotificationHelper::GetSyncNotificationEnabledWithoutApp(const int32_t u
         userId, enabled);
 }
 
-ErrCode NotificationHelper::SetBadgeNumber(int32_t badgeNumber, std::string instanceKey)
+ErrCode NotificationHelper::SetBadgeNumber(int32_t badgeNumber, const std::string &instanceKey)
 {
     return DelayedSingleton<AnsNotification>::GetInstance()->SetBadgeNumber(badgeNumber, instanceKey);
 }
diff --git a/frameworks/core/include/ans_notification.h b/frameworks/core/include/ans_notification.h
index 10d86a05afa49c51994793d2274b6e5b456c0cf0..1685a8d036536fca3ecabcb9e1a17b38979617af 100644
--- a/frameworks/core/include/ans_notification.h
+++ b/frameworks/core/include/ans_notification.h
@@ -134,7 +134,7 @@ public:
      *                This parameter must be specified.
      * @return Returns publish notification result.
      */
-    ErrCode PublishNotification(const NotificationRequest &request, std::string instanceKey = "");
+    ErrCode PublishNotification(const NotificationRequest &request, const std::string &instanceKey = "");
 
     /**
      * @brief Publishes a notification with a specified label.
@@ -147,7 +147,7 @@ public:
      * @return Returns publish notification result.
      */
     ErrCode PublishNotification(const std::string &label, const NotificationRequest &request,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Publishes a notification.
@@ -168,7 +168,7 @@ public:
      *                       Otherwise, this method does not take effect.
      * @return Returns cancel notification result.
      */
-    ErrCode CancelNotification(int32_t notificationId, std::string instanceKey = "");
+    ErrCode CancelNotification(int32_t notificationId, const std::string &instanceKey = "");
 
     /**
      * @brief Cancels a published notification matching the specified label and notificationId.
@@ -178,7 +178,7 @@ public:
      * @return Returns cancel notification result.
      */
     ErrCode CancelNotification(const std::string &label, int32_t notificationId,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Cancels all the published notifications.
@@ -186,7 +186,7 @@ public:
      *
      * @return Returns cancel all notifications result.
      */
-    ErrCode CancelAllNotifications(std::string instanceKey = "");
+    ErrCode CancelAllNotifications(const std::string &instanceKey = "");
 
     /**
      * @brief Cancels a published agent notification.
@@ -226,7 +226,7 @@ public:
      * @return Returns get active notifications result.
      */
     ErrCode GetActiveNotifications(std::vector<sptr<NotificationRequest>> &request,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Checks whether your application has permission to publish notifications by calling
@@ -734,7 +734,7 @@ public:
      * @param groupName the specified group name.
      * @return Returns cancel group result.
      */
-    ErrCode CancelGroup(const std::string &groupName, std::string instanceKey = "");
+    ErrCode CancelGroup(const std::string &groupName, const std::string &instanceKey = "");
 
     /**
      * @brief Removes the notification of the specified group of the specified application.
@@ -1010,7 +1010,7 @@ public:
      * @param badgeNumber The badge number.
      * @return Returns set badge number result.
      */
-    ErrCode SetBadgeNumber(int32_t badgeNumber, std::string instanceKey = "");
+    ErrCode SetBadgeNumber(int32_t badgeNumber, const std::string &instanceKey = "");
 
     /**
      * @brief Set badge number by bundle.
@@ -1324,7 +1324,6 @@ private:
     bool IsValidDelayTime(const NotificationRequest &request) const;
     void CreateSubscribeListener(const std::shared_ptr<NotificationSubscriber> &subscriber,
         sptr<SubscriberListener> &listener);
-    std::string GetAppInstanceKey() const;
 
 private:
     std::mutex subscriberMutex_;
diff --git a/frameworks/core/src/ans_notification.cpp b/frameworks/core/src/ans_notification.cpp
index 10024f68205b82b6d8504fef932847dea39d7765..ec0355a05fdfb7424bfc7deab68120da170db5ff 100644
--- a/frameworks/core/src/ans_notification.cpp
+++ b/frameworks/core/src/ans_notification.cpp
@@ -207,14 +207,14 @@ ErrCode AnsNotification::SetNotificationSlotFlagsAsBundle(const NotificationBund
     return proxy->SetSlotFlagsAsBundle(bo, validSlotFlag);
 }
 
-ErrCode AnsNotification::PublishNotification(const NotificationRequest &request, std::string instanceKey)
+ErrCode AnsNotification::PublishNotification(const NotificationRequest &request, const std::string &instanceKey)
 {
     ANS_LOGD("enter");
     return PublishNotification(std::string(), request, instanceKey);
 }
 
 ErrCode AnsNotification::PublishNotification(const std::string &label, const NotificationRequest &request,
-    std::string instanceKey)
+    const std::string &instanceKey)
 {
     HITRACE_METER_NAME(HITRACE_TAG_NOTIFICATION, __PRETTY_FUNCTION__);
     ANS_LOGI("PublishNotification,notificationId:%{public}u", request.GetNotificationId());
@@ -317,13 +317,13 @@ ErrCode AnsNotification::PublishNotificationForIndirectProxy(const NotificationR
     return proxy->PublishNotificationForIndirectProxy(reqPtr);
 }
 
-ErrCode AnsNotification::CancelNotification(int32_t notificationId, std::string instanceKey)
+ErrCode AnsNotification::CancelNotification(int32_t notificationId, const std::string &instanceKey)
 {
     return CancelNotification("", notificationId, instanceKey);
 }
 
 ErrCode AnsNotification::CancelNotification(const std::string &label, int32_t notificationId,
-    std::string instanceKey)
+    const std::string &instanceKey)
 {
     ANS_LOGI("enter CancelNotification,notificationId:%{public}d", notificationId);
     HITRACE_METER_NAME(HITRACE_TAG_NOTIFICATION, __PRETTY_FUNCTION__);
@@ -335,7 +335,7 @@ ErrCode AnsNotification::CancelNotification(const std::string &label, int32_t no
     return proxy->Cancel(notificationId, label, instanceKey);
 }
 
-ErrCode AnsNotification::CancelAllNotifications(std::string instanceKey)
+ErrCode AnsNotification::CancelAllNotifications(const std::string &instanceKey)
 {
     ANS_LOGI("CancelAllNotifications called.");
 
@@ -383,7 +383,7 @@ ErrCode AnsNotification::GetActiveNotificationNums(uint64_t &num)
 }
 
 ErrCode AnsNotification::GetActiveNotifications(std::vector<sptr<NotificationRequest>> &request,
-    std::string instanceKey)
+    const std::string &instanceKey)
 {
     sptr<IAnsManager> proxy = GetAnsManagerProxy();
     if (!proxy) {
@@ -1194,7 +1194,7 @@ ErrCode AnsNotification::GetShowBadgeEnabled(bool &enabled)
     return proxy->GetShowBadgeEnabled(enabled);
 }
 
-ErrCode AnsNotification::CancelGroup(const std::string &groupName, std::string instanceKey)
+ErrCode AnsNotification::CancelGroup(const std::string &groupName, const std::string &instanceKey)
 {
     ANS_LOGI("enter CancelGroup,groupName:%{public}s", groupName.c_str());
     if (groupName.empty()) {
@@ -1850,7 +1850,7 @@ ErrCode AnsNotification::GetSyncNotificationEnabledWithoutApp(const int32_t user
     return proxy->GetSyncNotificationEnabledWithoutApp(userId, enabled);
 }
 
-ErrCode AnsNotification::SetBadgeNumber(int32_t badgeNumber, std::string instanceKey)
+ErrCode AnsNotification::SetBadgeNumber(int32_t badgeNumber, const std::string &instanceKey)
 {
     sptr<IAnsManager> proxy = GetAnsManagerProxy();
     if (!proxy) {
@@ -2225,11 +2225,6 @@ ErrCode AnsNotification::UpdateNotificationTimerByUid(const int32_t uid, const b
     return proxy->UpdateNotificationTimerByUid(uid, isPaused);
 }
 
-std::string AnsNotification::GetAppInstanceKey() const
-{
-    return "";
-}
-
 ErrCode AnsNotification::DisableNotificationFeature(const NotificationDisable &notificationDisable)
 {
     ANS_LOGD("enter DisableNotificationFeature");
diff --git a/interfaces/inner_api/notification_helper.h b/interfaces/inner_api/notification_helper.h
index 0ba6ff992bfe3283d5085ef5044cf6ab012e1cdc..fc9bd295b3191c08770a0892a95e1bb38da51671 100644
--- a/interfaces/inner_api/notification_helper.h
+++ b/interfaces/inner_api/notification_helper.h
@@ -201,7 +201,7 @@ public:
      * @return Returns publish notification result.
      */
     static ErrCode PublishNotification(const NotificationRequest &request,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Publishes a notification.
@@ -225,7 +225,7 @@ public:
      * @return Returns publish notification result.
      */
     static ErrCode PublishNotification(const std::string &label, const NotificationRequest &request,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Cancels a published notification.
@@ -235,7 +235,7 @@ public:
      *                       Otherwise, this method does not take effect.
      * @return Returns cancel notification result.
      */
-    static ErrCode CancelNotification(int32_t notificationId, std::string instanceKey = "");
+    static ErrCode CancelNotification(int32_t notificationId, const std::string &instanceKey = "");
 
     /**
      * @brief Cancels a published notification matching the specified label and notificationId.
@@ -245,7 +245,7 @@ public:
      * @return Returns cancel notification result.
      */
     static ErrCode CancelNotification(const std::string &label, int32_t notificationId,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Cancels all the published notifications.
@@ -253,7 +253,7 @@ public:
      * @note To cancel a specified notification, see CancelNotification(int32_t).
      * @return Returns cancel all notifications result.
      */
-    static ErrCode CancelAllNotifications(std::string instanceKey = "");
+    static ErrCode CancelAllNotifications(const std::string &instanceKey = "");
 
     /**
      * @brief Cancels a published agent notification.
@@ -293,7 +293,7 @@ public:
      * @return Returns get active notifications result.
      */
     static ErrCode GetActiveNotifications(std::vector<sptr<NotificationRequest>> &request,
-        std::string instanceKey = "");
+        const std::string &instanceKey = "");
 
     /**
      * @brief Checks whether your application has permission to publish notifications by calling
@@ -775,7 +775,7 @@ public:
      * @param groupName Indicates the specified group name.
      * @return Returns cancel group result.
      */
-    static ErrCode CancelGroup(const std::string &groupName, std::string instanceKey = "");
+    static ErrCode CancelGroup(const std::string &groupName, const std::string &instanceKey = "");
 
     /**
      * @brief Remove the notification of the specified group of the specified application.
@@ -996,7 +996,7 @@ public:
      * @param badgeNumber The badge number.
      * @return Returns set badge number result.
      */
-    static ErrCode SetBadgeNumber(int32_t badgeNumber, std::string instanceKey = "");
+    static ErrCode SetBadgeNumber(int32_t badgeNumber, const std::string &instanceKey = "");
 
     /**
      * @brief Set badge number by bundle.