diff --git a/include/rtthread.h b/include/rtthread.h
index 1c78cbde43..393b40b1b6 100644
--- a/include/rtthread.h
+++ b/include/rtthread.h
@@ -601,12 +601,13 @@ void *rt_memcpy(void *dest, const void *src, rt_ubase_t n);
 char *rt_strdup(const char *s);
 
 #ifndef RT_KSERVICE_USING_STDLIB
-void *rt_memmove(void *dest, const void *src, rt_ubase_t n);
-rt_int32_t rt_memcmp(const void *cs, const void *ct, rt_ubase_t count);
+void *rt_memmove(void *dest, const void *src, rt_size_t n);
+rt_int32_t rt_memcmp(const void *cs, const void *ct, rt_size_t count);
 char *rt_strstr(const char *str1, const char *str2);
 rt_int32_t rt_strcasecmp(const char *a, const char *b);
-char *rt_strncpy(char *dest, const char *src, rt_ubase_t n);
-rt_int32_t rt_strncmp(const char *cs, const char *ct, rt_ubase_t count);
+char *rt_strcpy(char *dst, const char *src);
+char *rt_strncpy(char *dest, const char *src, rt_size_t n);
+rt_int32_t rt_strncmp(const char *cs, const char *ct, rt_size_t count);
 rt_int32_t rt_strcmp(const char *cs, const char *ct);
 rt_size_t rt_strlen(const char *src);
 #else
@@ -615,6 +616,7 @@ rt_size_t rt_strlen(const char *src);
 #define rt_memcmp(cs, ct, count)    memcmp(cs, ct, count)
 #define rt_strstr(str1, str2)       strstr(str1, str2)
 #define rt_strcasecmp(a, b)         strcasecmp(a, b)
+#define rt_strcpy(dest, src)        strcpy(dest, src)
 #define rt_strncpy(dest, src, n)    strncpy(dest, src, n)
 #define rt_strncmp(cs, ct, count)   strncmp(cs, ct, count)
 #define rt_strcmp(cs, ct)           strcmp(cs, ct)
diff --git a/src/kservice.c b/src/kservice.c
index a441124816..fa0da4c7c4 100644
--- a/src/kservice.c
+++ b/src/kservice.c
@@ -18,6 +18,7 @@
  * 2013-09-24     aozima       make sure the device is in STREAM mode when used by rt_kprintf.
  * 2015-07-06     Bernard      Add rt_assert_handler routine.
  * 2021-02-28     Meco Man     add RT_KSERVICE_USING_STDLIB
+ * 2021-12-20     Meco Man     implement rt_strcpy()
  */
 
 #include <rtthread.h>
@@ -300,7 +301,7 @@ RTM_EXPORT(rt_memcpy);
  *
  * @return The address of destination memory.
  */
-void *rt_memmove(void *dest, const void *src, rt_ubase_t n)
+void *rt_memmove(void *dest, const void *src, rt_size_t n)
 {
     char *tmp = (char *)dest, *s = (char *)src;
 
@@ -336,7 +337,7 @@ RTM_EXPORT(rt_memmove);
  *         If the result > 0, cs is greater than ct.
  *         If the result = 0, cs is equal to ct.
  */
-rt_int32_t rt_memcmp(const void *cs, const void *ct, rt_ubase_t count)
+rt_int32_t rt_memcmp(const void *cs, const void *ct, rt_size_t count)
 {
     const unsigned char *su1, *su2;
     int res = 0;
@@ -421,7 +422,7 @@ RTM_EXPORT(rt_strcasecmp);
  *
  * @return The address where the copied content is stored.
  */
-char *rt_strncpy(char *dst, const char *src, rt_ubase_t n)
+char *rt_strncpy(char *dst, const char *src, rt_size_t n)
 {
     if (n != 0)
     {
@@ -444,6 +445,21 @@ char *rt_strncpy(char *dst, const char *src, rt_ubase_t n)
 }
 RTM_EXPORT(rt_strncpy);
 
+/**
+ * This function will copy string.
+ *
+ * @param  dst points to the address used to store the copied content.
+ *
+ * @param  src is the string to be copied.
+ *
+ * @return The address where the copied content is stored.
+ */
+char *rt_strcpy(char *dst, const char *src)
+{
+    return rt_strncpy(dst, src, (rt_size_t)-1);
+}
+RTM_EXPORT(rt_strcpy);
+
 /**
  * This function will compare two strings with specified maximum length.
  *
@@ -458,7 +474,7 @@ RTM_EXPORT(rt_strncpy);
  *         If the result > 0, cs is greater than ct.
  *         If the result = 0, cs is equal to ct.
  */
-rt_int32_t rt_strncmp(const char *cs, const char *ct, rt_ubase_t count)
+rt_int32_t rt_strncmp(const char *cs, const char *ct, rt_size_t count)
 {
     register signed char __res = 0;