diff --git a/rt-thread-version/rt-thread-standard/programming-manual/device/pulse_encoder/pulse_encoder.md b/rt-thread-version/rt-thread-standard/programming-manual/device/pulse_encoder/pulse_encoder.md
index 286f2a5c08a581047ae7500adeb5ab64eb8559aa..332d2bd07ea160593a86c0376ea411d0dad585a2 100644
--- a/rt-thread-version/rt-thread-standard/programming-manual/device/pulse_encoder/pulse_encoder.md
+++ b/rt-thread-version/rt-thread-standard/programming-manual/device/pulse_encoder/pulse_encoder.md
@@ -185,7 +185,7 @@ static int pulse_encoder_sample(int argc, char *argv[])
 {
     rt_err_t ret = RT_EOK;
     rt_device_t pulse_encoder_dev = RT_NULL;   /* 脉冲编码器设备句柄 */
-
+    rt_uint32_t index;
     rt_int32_t count;
 
     /* 查找脉冲编码器设备 */
@@ -204,7 +204,7 @@ static int pulse_encoder_sample(int argc, char *argv[])
         return ret;
     }
 
-    for(rt_uint32 i; i <= 10; i++)
+    for (index = 0; index <= 10; index ++)
     {
         rt_thread_mdelay(500);
         /* 读取脉冲编码器计数值 */