diff --git a/src/connector/C#/src/TDengineDriver/TDengineDriver.cs b/src/connector/C#/src/TDengineDriver/TDengineDriver.cs
index 8b53bda5622945f2dfb27dc5426ab96e9dbe9be5..193428fe8f5e75916ae4d301b9b2035afb3557f6 100644
--- a/src/connector/C#/src/TDengineDriver/TDengineDriver.cs
+++ b/src/connector/C#/src/TDengineDriver/TDengineDriver.cs
@@ -235,6 +235,7 @@ namespace TDengineDriver
 
             IntPtr commandBuffer = Marshal.StringToCoTaskMemUTF8(command);
             res = Query(conn, commandBuffer);
+            Marshal.FreeCoTaskMem(commandBuffer);
             return res;
         }