This paper discusses the characteristics of welding power supply, and then gives the design ideas of digital welding power. A full-bridge configuration which cooperates with high frequency transformer and rectifier circuit is used to be main circuit, and IGBT is the primary switch component. The leading leg achieves Zero Voltage Switching, and the lagging leg is Zero Current Switching by the combination of soft switching and inverter technology. We take UC3879 as the core of PWM controlling to carry out soft switching and TMS320LF2407A as the core of all controlling system. The control strategy adopts fuzzy-PID control.