Abstract: A feed switch protection system in the coal mine based on STM32F407 chip is designed. The system has protection functions such as leakage, overcurrent, and short circuit. The system design uses a modular design method, combining the advantages and disadvantages of various current protection methods in coal mines. According to the different characteristics of leakage, short circuit and overload in coal mines, different detection methods are used, such as three-phase short circuit protection. The system uses a combination of amplitude detection and phase-sensitive detection. It uses negative sequence detection for asynchronous motors and lines for phase failures and phase-to-phase short circuits. In terms of overload protection, the definite-time protection and the inverse-time protection curve are combined. Different voltage levels give specific parameter setting values for each module. Experiments verify the reliability and stability of the system.