diff --git a/observer_agent/grpc_comm/client.cpp b/observer_agent/grpc_comm/client.cpp
index ecb54aedaf5e1d72323105bf15fbc4ff05c3c5da..84b5c96ccd38493f9702eb748aac24e4990ae569 100644
--- a/observer_agent/grpc_comm/client.cpp
+++ b/observer_agent/grpc_comm/client.cpp
@@ -43,16 +43,22 @@ std::unique_ptr<ClientReader<Message>> PubSubClient::Subscribe(const int topic)
     SubscribeRequest request;
     request.set_topic(topic);
     request.set_sub_name(uuid_str);
+    std::string ret_info;
 
     Message msg;
     SubFlag = true;
     std::unique_ptr<ClientReader<Message>> reader = stub_->Subscribe(&context, request);
-    if (reader == nullptr)
+    ret_info = ReadFrom(reader);
+
+    if (ret_info.substr(0, 6) == "topic:")
+    {
+        std::cout << "Success subscribe." << std::endl;
+        return reader;
+    } else
     {
         std::cerr << "Failed to subscribe." << std::endl;
         return nullptr;
     }
-    return reader;
 }
 
 void PubSubClient::Publish(const int topic, const std::string &content)
diff --git a/observer_agent/grpc_comm/server.cpp b/observer_agent/grpc_comm/server.cpp
index 54ae66fe1db95ebbfddd18b8a7b3f34f5bd59c0a..d53866fe0c22303e755f972169fc7a265379f34e 100644
--- a/observer_agent/grpc_comm/server.cpp
+++ b/observer_agent/grpc_comm/server.cpp
@@ -86,6 +86,14 @@ class PubSubServiceImpl final : public SubManager::Service
             return grpc::Status(grpc::StatusCode::INTERNAL, "multi-process max connection number, Failed to Subscribe the topic");
         }
 
+        msg.set_text("topic: " + std::to_string(cli_topic) + " Subscribe success!");
+        if (!writer->Write(msg))
+        {
+            std::cerr << "Failed to write the initial message" << std::endl;
+            sub_mutex.unlock();
+            return grpc::Status(grpc::StatusCode::INTERNAL, "Failed to write the message");
+        }
+
         suber_topic_[cli_name].push_back(cli_topic);
         suber_writer_[cli_name].push_back(writer);
         suber_connection_[cli_name].push_back(tmp_index);
@@ -94,13 +102,6 @@ class PubSubServiceImpl final : public SubManager::Service
 
         sub_mutex.unlock();
 
-        msg.set_text("topic: " + std::to_string(cli_topic) + " Subscribe success!");
-        if (!writer->Write(msg))
-        {
-            std::cerr << "Failed to write the initial message" << std::endl;
-            return grpc::Status(grpc::StatusCode::INTERNAL, "Failed to write the message");
-        }
-
         keepalive_msg.set_text("keepalive");
         while (connect_status[tmp_index])
         {