diff --git a/paddle/fluid/string/string_helper_test.cc b/paddle/fluid/string/string_helper_test.cc
index deeb4bdcc829179f10669d716d26284bac9f5e8f..4796bf7507aba7f8afac06dc33f08c7025b33d4b 100644
--- a/paddle/fluid/string/string_helper_test.cc
+++ b/paddle/fluid/string/string_helper_test.cc
@@ -33,10 +33,10 @@ TEST(StringHelper, EndsWith) {
 
 TEST(StringHelper, FormatStringAppend) {
   std::string str("hello");
-  char fmt[] = "hhh";
+  char fmt[] = "%d";
 
-  paddle::string::format_string_append(str, fmt);
-  EXPECT_EQ(str, "hellohhh");
+  paddle::string::format_string_append(str, fmt, 10);
+  EXPECT_EQ(str, "hello10");
 }
 
 TEST(StringHelper, JoinStrings) {