diff --git a/paddle/fluid/string/piece.cc b/paddle/fluid/string/piece.cc
index 454f5d8d38c5f02598cddaab555334a1e8a398da..8e8cfb0e91389490895835ed09ef36adf756d3ca 100644
--- a/paddle/fluid/string/piece.cc
+++ b/paddle/fluid/string/piece.cc
@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#include "piece.h"
+#include "paddle/fluid/string/piece.h"
 
 #include <string.h>
 
diff --git a/paddle/fluid/string/printf.h b/paddle/fluid/string/printf.h
index 693cf9d6dfeea0735801e64fe74b9770c258c553..062095a1c3e977c0bcc89346ead765acb023bcf7 100644
--- a/paddle/fluid/string/printf.h
+++ b/paddle/fluid/string/printf.h
@@ -71,6 +71,8 @@
 
 #include <iostream>
 #include <sstream>
+#include <string>
+
 #include "tinyformat/tinyformat.h"  // https://github.com/c42f/tinyformat
 
 namespace paddle {
diff --git a/paddle/fluid/string/printf_test.cc b/paddle/fluid/string/printf_test.cc
index b6a60c8d6b7f15f8e5572cf5bb1e7f04ee1c1598..678029f93534ab374bd29083f8991d632ccdd5a1 100644
--- a/paddle/fluid/string/printf_test.cc
+++ b/paddle/fluid/string/printf_test.cc
@@ -11,7 +11,8 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
-#include "printf.h"
+
+#include "paddle/fluid/string/printf.h"
 
 #include <string>
 
@@ -21,7 +22,7 @@ TEST(StringPrintf, StringPrintf) {
   std::string weekday = "Wednesday";
   const char* month = "July";
   size_t day = 27;
-  long hour = 14;
+  int hour = 14;
   int min = 44;
   EXPECT_EQ(std::string("Wednesday, July 27, 14:44"),
             paddle::string::Sprintf("%s, %s %d, %.2d:%.2d", weekday, month, day,
diff --git a/paddle/fluid/string/to_string_test.cc b/paddle/fluid/string/to_string_test.cc
index 8fc293af0e473994ac13f6615d3f6195c8c5f04c..1d9c0e5e0c2b6e7f44c1622d2828b21b0a4380ee 100644
--- a/paddle/fluid/string/to_string_test.cc
+++ b/paddle/fluid/string/to_string_test.cc
@@ -12,7 +12,7 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License. */
 
-#include "to_string.h"
+#include "paddle/fluid/string/to_string.h"
 #include <gtest/gtest.h>
 
 constexpr char kOutputString[] = "User Defined Output";
@@ -26,14 +26,13 @@ std::ostream& operator<<(std::ostream& s, const UserDefinedClass& ins) {
 }
 
 TEST(to_string, normal) {
-  using namespace paddle::string;
+  using paddle::string::to_string;
   ASSERT_EQ("10", to_string(10));
   ASSERT_EQ("abc", to_string("abc"));
   ASSERT_EQ("1.2", to_string(1.2));
 }
 
 TEST(to_string, user_defined) {
-  using namespace paddle::string;
   UserDefinedClass instance;
-  ASSERT_EQ(kOutputString, to_string(instance));
+  ASSERT_EQ(kOutputString, paddle::string::to_string(instance));
 }