Abstract: Hot galvanization steel with high strength was widely applied in auto body manufacturing because of its high strength and good corrosion resistance, but it had serious electrode wear and obvious pitting change in spot welding, which had great effect on nugget formation.FEA model of pitting was established during spot welding to study the effect of pitting on nugget formation and corresponding experiments were carried out.It was shown that the growth of pitting increased real contact area between parts, which decreased current density and reduced nugget diameter.Compared with pitting produced at edge region of electrode surface, the pitting produced at center region was more disadvantageous for the nugget formation.Ring-nugget would be formed with the pitting area being increased.