diff --git a/doc/fluid/design/concepts/functions_operators_layers.md b/doc/fluid/design/concepts/functions_operators_layers.md
index 30bc488a18a28d349645d9d2502aae6691a69931..1f86b99e5197c3e0b85fd76fe704520ef21b06d3 100644
--- a/doc/fluid/design/concepts/functions_operators_layers.md
+++ b/doc/fluid/design/concepts/functions_operators_layers.md
@@ -40,7 +40,7 @@ template <typename T>
 class FCOp : public OperatorBase {
  public:
   void Run(...) {
-    add(mul(Input<T>("X"), Input<T>("W")), Input<T>("b");
+    add(mul(Input<T>("X"), Input<T>("W")), Input<T>("b"));
   }
 };
 REGISTER_OP(FCOp, "fc");