A　new　20　kHz　frequence　resistance　welding　inverter　was　designed.　In　this　unit　IGBT　was　adopted　as　switching　element.　A　single　line　and　double　inductance　rectified　commute　circuit　was　used.　In　addition,　the　electron　elements　were　made　full　use,　the　inverter　power　source　has　many　advantages　such　as　saving　energy,　smaller,　lighter　and　responding　rapidly,　further　more　the　efficiency　of　the　inverter　was　improved.