add requirement
@@ -7,7 +7,7 @@ PaddleStructure is an OCR toolkit for complex layout analysis. It can divide doc
**install layoutparser**
```sh
-pip3 install -U https://paddleocr.bj.bcebos.com/whl/layoutparser-0.0.0-py3-none-any.whl
+pip3 install -U premailer paddleocr https://paddleocr.bj.bcebos.com/whl/layoutparser-0.0.0-py3-none-any.whl
```
**install paddlestructure**
