diff --git a/components/libc/compilers/common/unistd.c b/components/libc/compilers/common/unistd.c
index 6c81fc76626a326ac3ef900fa8e62cd3bf69cd82..4385643f31e331557808a1f7dc9097e05c445ca8 100644
--- a/components/libc/compilers/common/unistd.c
+++ b/components/libc/compilers/common/unistd.c
@@ -55,7 +55,14 @@ RTM_EXPORT(sleep);
 
 int usleep(useconds_t usec)
 {
-    rt_thread_mdelay(usec / 1000u);
+    if (rt_thread_self() != RT_NULL)
+    {
+        rt_thread_mdelay(usec / 1000u);
+    }
+    else
+    {
+        rt_hw_us_delay(usec / 1000u);
+    }
     rt_hw_us_delay(usec % 1000u);
     return 0;
 }