ln lndustrial production.it often encounts problems In updating program of MCU(Micro Controller Unit),and the process parameters can not be updated as needed in real time.in order to facilitate the online updates of STM8 microcontroller,the paper designed u STM8 onHne downloader based on STM32 microcontroller and SWIM protoc01.The downloader does not rely on a eomputer or u dedicated download device.It has a simple eurcuit structure。 and is easy to download online.accurately and fastly.When STM32 connects to a touch screen.the downloader Call modify parameters online.Through practical application.the downloader has achieved agood result.