It is very difficult for arc welding inverter to realize Zero-Voltage-Switching (ZVS) because the load of arc welding inverter changes violently. An improved PS-FB-ZVS-PWM (Phase-Shifted Full-Bridge Zero-Voltage-Switching Pulse-WidthModulation) topology is proposed in this paper. A saturate resonant inductor is in series with the primary side of the transformer, while an auxiliary inductor is in parallel with the secondary side of the transformer to increase reactive current in light load or unload state, so the zero voltage switching of power devices is realized during switching course in light load or unload state.