There are many kinds of sensors in coal mine，especially gas，air volume，roof pressure and other sensors，which play an important role in safety warning. In order to make the software of sensors easy to maintain，this paper puts forward an upgrade system of underground sensors based on STM32. The principle of scattered loading of target code by MCU and other key technologies such as breakpoint continuation are mainly used. Practice has proved that the system can solve the problem of updating and replacing the downhole sensor software without losing safety.