diff --git a/api/@ohos.systemParameterV9.d.ts b/api/@ohos.systemParameterV9.d.ts
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+/*
+ * Copyright (c) 2021 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { AsyncCallback, BusinessError } from './basic';
+
+/**
+ * Enumerates error code.
+ *
+ * @since 9
+ */
+export enum SystemParameterErrorCode {
+    /**
+     * Input parameter is missing or invalid.
+     *
+     * @since 9
+     */
+    SYSPARAM_INVALID_INPUT = 401,
+
+    /**
+     * System parameter can not be found.</br>
+     * When getting system parameter values, if def value is specified, it will not return this error.
+     *
+     * @since 9
+     */
+    SYSPARAM_NOT_FOUND = 14700101,
+
+    /**
+     * System parameter value is invalid.</br>
+     *   - <p>When setting system parameters, the value length should not exceed 95 bytes.</p>
+     *   - <p>And system parameter has three value types: string, integer and bool.
+     *     if the value type is not matched, it will also return this error code.</p>
+     *
+     * @since 9
+     */
+    SYSPARAM_INVALID_VALUE = 14700102,
+
+    /**
+     * System permission operation permission denied.</br>
+     * <p>System parameter are system resources, each parameter is protected by DAC and MAC rules.
+     * <p>Typical permission checking include:</p>
+     *   - <p>systemapi: only system application can call system parameter related APIs</p>
+     *   - <p>DAC: each system parameter has user and group owner with get, set permissions.
+    *           Applications can only operate User/Group/Ownership matched system parameters.</p>
+     *   - <p>MAC: each system parameter is also protected by SELinux labels.</p>
+     *
+     * @since 9
+     */
+    SYSPARAM_PERMISSION_DENIED = 14700103,
+
+    /**
+     * System internal error including out of memory, deadlock etc.
+     *
+     * @since 9
+     */
+    SYSPARAM_SYSTEM_ERROR = 14700104,
+}
+
+ /**
+ * The interface of system parameters class.
+ *
+ * @since 9
+ * @syscap SystemCapability.Startup.SystemInfo
+ * @systemapi Hide this for inner system use.
+ */
+declare namespace systemParameterV9 {
+    /**
+     * Gets the value of the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param def Default value.
+     * @return the value of the parameter.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_NOT_FOUND if key is not found
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function getSync(key: string, def?: string): string;
+
+    /**
+     * Gets the value of the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param callback Callback function.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_NOT_FOUND if key is not found
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function get(key: string, callback: AsyncCallback<string>): void;
+
+    /**
+     * Gets the value of the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param def Default value.
+     * @param callback Callback function.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_NOT_FOUND if key is not found
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function get(key: string, def: string, callback: AsyncCallback<string>): void;
+
+    /**
+     * Gets the value of the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param def Default value.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_NOT_FOUND if key is not found
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @return Promise, which is used to obtain the result asynchronously.
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function get(key: string, def?: string): Promise<string>;
+
+    /**
+     * Sets a value for the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param value System attribute value to set.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_INVALID_VALUE if value is invalid
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function setSync(key: string, value: string): void;
+
+    /**
+     * Sets a value for the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param value System attribute value to set.
+     * @param callback Callback function.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_INVALID_VALUE if value is invalid
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function set(key: string, value: string, callback: AsyncCallback<void>): void;
+
+    /**
+     * Sets a value for the attribute with the specified key.
+     *
+     * @param key Key of the system attribute.
+     * @param value Default value.
+     * @return Promise, which is used to obtain the result asynchronously.
+     * @throws {BusinessError} with SYSPARAM_INVALID_INPUT if type of key is not string or key is not specified.
+     * @throws {BusinessError} with SYSPARAM_INVALID_VALUE if value is invalid
+     * @throws {BusinessError} with SYSPARAM_PERMISSION_DENIED if permission denied
+     * @throws {BusinessError} with SYSPARAM_SYSTEM_ERROR if system internal error
+     * @syscap SystemCapability.Startup.SystemInfo
+     * @since 9
+     */
+    function set(key: string, value: string): Promise<void>;
+}
+
+export default systemParameter;