Abstract: In allusion to problems of big harmonic content of input circuit and low power factor existing in traditional switching power supply which uses uncontrollable diode or phase-controlled thyristor for rectification, the paper proposed two design schemes of switching power supply with high power factor, analyzed principle of improving power factor by APFC technology and PWM rectifier technology, and used Matlab7.6 to simulate APFC circuit and voltage mode PWM rectifying circuit of single-phase full-bridge. The simulation result showed that the switching power supply based on PWM rectifier technology can improve power factor and reduce harmonic current.