Abstract: An integrated protector of electromagnetic starter and lighting signal is designed for underground coal mine in this paper. Based on the STM32 microcontroller and its internal digital-to-analog conversion module, the protector can obtain the real-time operating status of the protected equipment, and protect the electric motor, lighting and signal system of underground coal mine at the same time. The protector has multiple functions including the leakage lockout, excessive gas concentration lock in the wind power circuit, failure information storage, the danger indication of overload, short circuit, under-voltage, over-voltage, phase failure, three-phase imbalance and insulation, etc. Moreover, the protector has the advantages of high detection accuracy, strong anti-interference ability, fast response speed, convenient operation and low maintenance cost.