Abstract: The circuit of mine intrinsically safe equipment has the risk of short-circuit failure, the chip surface temperature in current-limiting start circuit rises sharply, and the excessively high surface temperature of device leads to the failure of the startup circuit and the risk of safety. Aiming at these problems, this paper introduces the design of a startup protection circuit based on thermistor, gives the circuit principle, analyzes the working characteristics of the circuit, and carries out the heat transfer analysis and design of discontinuous medium. The working performance test of the temperature protection circuit and the heat transfer performance test of the discontinuous medium verify the validity and reliability of the circuit.