Abstract: A new kind of arc voltage feedback system is designed,which keep the average voltage of every cycle time constant,and the arclength could be regulated stably.The control system is completed by soft-ware,and interface is friendly.In order to ensure transfer made of a dropper pulse,the pulse parameters are optimized.It is demonstrated that the welding procedure is stable and there is hardly any spatter;the appearance of the bead is beautiful.The designed pulsed metal inre-gas arcwelding machine has been put into production.