diff --git a/src/main/java/com/loafle/commons/rpc/protocol/grpc/GRPCServerRequestCodec.java b/src/main/java/com/loafle/commons/rpc/protocol/grpc/GRPCServerRequestCodec.java
index 601d205..99d524d 100644
--- a/src/main/java/com/loafle/commons/rpc/protocol/grpc/GRPCServerRequestCodec.java
+++ b/src/main/java/com/loafle/commons/rpc/protocol/grpc/GRPCServerRequestCodec.java
@@ -48,6 +48,11 @@ class GRPCServerRequestCodec implements RPCRegistryCodec {
       Type paramType = paramTypes[i];
       String param = this.params.get(i).toStringUtf8();
 
+      if (paramType.equals(String.class)) {
+        result[i] = param;
+        continue;
+      }
+
       result[i] = this.gson.fromJson(param, paramType);
     }