A man machine interactive system, which is based on USART of STM32 and applied to new automatic weather station of DZZ12, is designed. Through this interactive system, the user can directly and conveniently set parameters or view data in the installation and maintenance for the new automatic weather station. This design includes hardware circuit design, user UI design and embedded software design. The design flow of user UI and the key points of the USART interrupt function are described emphatically. It proves that the system is stable and reliable after testing and business operation for one year in Guangdong Province.