Abstract: For problems of existing mine-used switching power supply such as large harmonic current, low power factor and so on, a mine-used switching power supply was designed by use of technologies of active power factor correction and resonant soft switching. Design indexes of the power supply were introduced as well as design scheme of its hardware circuits. The test results show that under conditions of inputting AC170 V and outputting full load, the inputting current of the power supply has no pulse and little harmonic current; the max temperature of main components of the power supply is 98.5 ℃ when environmental temperature is 50 ℃; when input voltage is AC90~265 V, power factor of the power supply is not less than 0.96, ripple voltage is less than 30 mV, and efficiency is 86.5%; in test of insulation withstand voltage, insulation resistance is not less than 50 MΩ, and leakage current is less than 1 mA.