Abstract: A new type of power MOSFET inverter for arc welding with its performance indices is introduced in this paper.The inverter for micro-beam plasma arc welding and GTAW is developed by authors in GFR.As a result of experiment and research,it was found that by use of new type of power MOSFET as a substitute for power bipolar-transistor as rapid switch,this inverter for arc welding possesses the following advantages:the operation range reliable is wider,working frequency and efficiency are higher,the dimentions of the inverter are smaller,control power is minimal,microprocessor can be used for control.In view of the main difficulty in developing this inverter,some notable problems in design and manufacture are described,and the developing prospect of this type of inverter is also predicted in this paper.