diff --git a/docs/tutorial-12-mysql_cli.md b/docs/tutorial-12-mysql_cli.md
index 707315487a..04ba71ca96 100644
--- a/docs/tutorial-12-mysql_cli.md
+++ b/docs/tutorial-12-mysql_cli.md
@@ -266,7 +266,7 @@ WFMySQLConnection相当于一个二级工厂，我们约定任何工厂对象的
 ~~~cpp
     WFMySQLConnection *conn = new WFMySQLConnection(1234);
     conn->init(url);
-	auto *task = conn->create_query_task("SELECT * from table", my_callback);
+    auto *task = conn->create_query_task("SELECT * from table", my_callback);
     conn->deinit();
     delete conn;
     task->start();