diff --git a/components/utilities/ymodem/ymodem.c b/components/utilities/ymodem/ymodem.c
index 164342964741a8c104326abb8d7cc9be041ebc34..a1f21cf6c64c3902c5fda96105f5a634c8af16eb 100644
--- a/components/utilities/ymodem/ymodem.c
+++ b/components/utilities/ymodem/ymodem.c
@@ -122,6 +122,7 @@ static rt_err_t _rym_do_handshake(
     enum rym_code code;
     rt_size_t i;
     rt_uint16_t recv_crc, cal_crc;
+    rt_size_t data_sz;
 
     ctx->stage = RYM_STAGE_ESTABLISHING;
     /* send C every second, so the sender could know we are waiting for it. */
@@ -131,26 +132,36 @@ static rt_err_t _rym_do_handshake(
         code = _rym_read_code(ctx,
                 RYM_CHD_INTV_TICK);
         if (code == RYM_CODE_SOH)
+        {
+            data_sz = _RYM_SOH_PKG_SZ;
+            break;
+        }
+        else if(code == RYM_CODE_STX)
+        {
+            data_sz = _RYM_STX_PKG_SZ;
             break;
+        }
     }
     if (i == tm_sec)
+    {
         return -RYM_ERR_TMO;
+    }
 
-    i = _rym_read_data(ctx, _RYM_SOH_PKG_SZ-1);
-    if (i != (_RYM_SOH_PKG_SZ-1))
+    i = _rym_read_data(ctx, data_sz-1);
+    if (i != (data_sz-1))
         return -RYM_ERR_DSZ;
 
     /* sanity check */
     if (ctx->buf[1] != 0 || ctx->buf[2] != 0xFF)
         return -RYM_ERR_SEQ;
 
-    recv_crc = (rt_uint16_t)(*(ctx->buf+_RYM_SOH_PKG_SZ-2) << 8) | *(ctx->buf+_RYM_SOH_PKG_SZ-1);
-    cal_crc = CRC16(ctx->buf+3, _RYM_SOH_PKG_SZ-5);
+    recv_crc = (rt_uint16_t)(*(ctx->buf+data_sz-2) << 8) | *(ctx->buf+data_sz-1);
+    cal_crc = CRC16(ctx->buf+3, data_sz-5);
     if (recv_crc != cal_crc)
         return -RYM_ERR_CRC;
 
     /* congratulations, check passed. */
-    if (ctx->on_begin && ctx->on_begin(ctx, ctx->buf+3, 128) != RYM_CODE_ACK)
+    if (ctx->on_begin && ctx->on_begin(ctx, ctx->buf+3, data_sz-5) != RYM_CODE_ACK)
         return -RYM_ERR_CAN;
 
     return RT_EOK;