diff --git a/include/rtthread.h b/include/rtthread.h
index 5309c31d5aa2a9fbba6ca9b76d0e55a402e8c27f..9bb02abedefe70194d472f88f747d845488c355f 100644
--- a/include/rtthread.h
+++ b/include/rtthread.h
@@ -501,9 +501,9 @@ int *_rt_errno(void);
 void *rt_memset(void *src, int c, rt_ubase_t n);
 void *rt_memcpy(void *dest, const void *src, rt_ubase_t n);
 
-rt_ubase_t rt_strncmp(const char *cs, const char *ct, rt_ubase_t count);
-rt_ubase_t rt_strcmp (const char *cs, const char *ct);
-rt_ubase_t rt_strlen (const char *src);
+rt_int32_t rt_strncmp(const char *cs, const char *ct, rt_ubase_t count);
+rt_int32_t rt_strcmp (const char *cs, const char *ct);
+rt_size_t rt_strlen (const char *src);
 char *rt_strdup(const char *s);
 
 char *rt_strstr(const char *str1, const char *str2);
diff --git a/src/kservice.c b/src/kservice.c
index b5dc92b09131ce144ce57dfd96b8bcc63842c842..ab15917bbe33aeca65f047986df13facb1677568 100644
--- a/src/kservice.c
+++ b/src/kservice.c
@@ -430,7 +430,7 @@ RTM_EXPORT(rt_strncpy);
  *
  * @return the result
  */
-rt_ubase_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_ubase_t count)
 {
     register signed char __res = 0;
 
@@ -453,7 +453,7 @@ RTM_EXPORT(rt_strncmp);
  *
  * @return the result
  */
-rt_ubase_t rt_strcmp(const char *cs, const char *ct)
+rt_int32_t rt_strcmp(const char *cs, const char *ct)
 {
     while (*cs && *cs == *ct)
         cs++, ct++;
@@ -470,7 +470,7 @@ RTM_EXPORT(rt_strcmp);
  *
  * @return the length of string
  */
-rt_ubase_t rt_strlen(const char *s)
+rt_size_t rt_strlen(const char *s)
 {
     const char *sc;