The technology of soft-switching can improve stability ,reliability and efficiency of the inverting spot welding power supply .In this paper ,a new kind of topology of zero-voltage switching spot welding power supply is proposed ,which is auxiliary circuit in paralleling with the lagging lag ,so it can afford auxiliary current of soft switch .With the relationship between circuit state of every working mode of main circuit and main circuit parameters in new topology ,the ability of searching optimal overall situation of ACA is used to optimize circuit parameters ,and it turns out to confirm the advantage of this topology .