diff --git a/components/libc/compilers/armlibc/syscalls.c b/components/libc/compilers/armlibc/syscalls.c
index bef92599d6401ee930e38fb68874226ee48bcd3f..2c53310771f1ef5ab164f3aa17f55f2fa082a027 100644
--- a/components/libc/compilers/armlibc/syscalls.c
+++ b/components/libc/compilers/armlibc/syscalls.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006-2021, RT-Thread Development Team
+ * Copyright (c) 2006-2022, RT-Thread Development Team
  *
  * SPDX-License-Identifier: Apache-2.0
  *
@@ -226,6 +226,11 @@ int _sys_write(FILEHANDLE fh, const unsigned char *buf, unsigned len, int mode)
         size = write(fh, buf, len);
         if (size >= 0)
         {
+            /*
+            fflush doesn't have a good solution in Keil-MDK,
+            so it has to sync/flush when for each writen.
+            */
+            fsync(fh);
             return len - size; /* success */
         }
         else
@@ -239,6 +244,18 @@ int _sys_write(FILEHANDLE fh, const unsigned char *buf, unsigned len, int mode)
     }
 }
 
+/*
+ * Flush any OS buffers associated with fh, ensuring that the file
+ * is up to date on disk. Result is >=0 if OK, negative for an
+ * error.
+ * This function is deprecated. It is never called by any other library function,
+ * and you are not required to re-implement it if you are retargeting standard I/O (stdio).
+ */
+int _sys_ensure(FILEHANDLE fh)
+{
+    return fsync(fh);
+}
+
 /*
  * Move the file position to a given offset from the file start.
  * Returns >=0 on success, <0 on failure.