Abstract: High voltage intrinsic safety power source plays a vital role in coal mine cable fault diagnosis, but there are defects in using the traditional intrinsic safety power limiting circuit. We introduce a new type of overcurrent protection circuit for high-voltage intrinsic safety power source, analyze the working principle of the circuit, and compare with the traditional methods. The circuit has a better protection than traditional methods validated in actual application, and the circuit is simple, reliable, easy to debug, which provides condition for the design of the high voltage intrinsic safety power source.