diff --git a/zh-cn/application-dev/device/usb-guidelines.md b/zh-cn/application-dev/device/usb-guidelines.md
index 6c412ce6a96b31e49e1c9e08dc78c395dd05552b..02d8a4ba5691c51289c880ba72c515aed1fa479e 100644
--- a/zh-cn/application-dev/device/usb-guidelines.md
+++ b/zh-cn/application-dev/device/usb-guidelines.md
@@ -135,7 +135,7 @@ USB设备可作为Host设备连接Device设备进行数据传输。开发示例
    let dataUint8Array = new Uint8Array(1024);
    usb.bulkTransfer(pipe, inEndpoint, dataUint8Array, 15000).then(dataLength => {
    if (dataLength >= 0) {
-     console.info("usb readData buffer : " + resultStr);
+     console.info("usb readData result Length : " + dataLength);
    } else {
      console.info("usb readData failed : " + dataLength);
    }