Abstract: In view of problems of simple protection function, low conversion efficiency, poor anti-interference ability and low intrinsic safety current existed in current protection module of intrinsic safety power supply, a protection module of intrinsic safety power supply based on surge suppressor LT4356 was designed. Function realization principle of the module was analyzed, including soft start, over-voltage, over-current and voltage sag protection, protection locking. The module with output voltage is DC5-18 V, the maximum current is 850-1 000 mA and fault protection time within 2 μs, which meets intrinsic safety requirements of GB 3836.4-2010.