Abstract: SiC-based power devices have the advantages of fast switching speed, low switching loss, and small conduction loss, which are conducive to further improving the inverter frequency and response speed of the welding power supply, achieving precise control of arc energy. A set of pulsed variable polarity inverter welding power supply is designed. The main circuit adopts a dual inverter structure. The front-stage high-frequency inverter circuit adopts SiC-based power modules, and the latter-stage low-frequency inverter circuit adopts IGBT modules. The SiC-based module driving circuit is designed, and fast short-circuit protection and miller clamp are realized. A full digital control system based on ARM (advanced RISC machines) is designed, and the digital control of PWM and output current waveform is realized. The developed pulsed variable polarity welding power supply has an inverter frequency of 100 kHz and a rated output current of 500 A, which can achieve a regular current output of pulsed variable polarity waveform. The results show that the developed pulsed variable polarity inverter welding power supply can achieve a stable welding process, and can effectively control the welding heat input through the adjustment of waveform parameters to obtain an excellent magnesium alloy weld formation.