A UC3842-based PFC converter is designed by means of dual-transistor forward single stage PFC topological structure and multiplex MOSFET switch, and the system structure, main circuit work principle and drive circuit are introduced. Through the measurements of the prototype, the output voltage of 48 V and the output power of 100 W are obtained. The voltage between the two poles of the energy storage capacitor is controlled within the allowable range and the electrical isolation between the input and output is achieved. The testing result indicates that the performance index of the prototype meets the design requirements.