Abstract: This paper studies and anaiysis mathematicallg the main circuit topologies of the modern gemeration of arc welding inverters using IGBT,MOSFET as power semiconductor device.Based on the circuit-level mathematical models set up in this paper,the characteristics of four popular and typical main circuit topoplogies are explored deeply and the expressions of the output power and the average current through the power semiconductor switching devices in each topologies are derived out, and some singnificant conclutions are obtained.