Abstract: The wear of electrode end face causes its diameter to increase, the current density of welding surface decreases, and the welding spot quality decreases, which seriously affects the quality of automobile body.Taking 0.6 mm thick galvanized steel sheet as the research object, the step-up mechanism parameters were set, and a comparison analysis of the wear of the end face of the electrode and the quality of the solder joint before and after the application of the step-up mechanism was carried out. The results show that under the step-up mechanism, with the welding process continues, the welding current increases, the electrode end diameter increases faster, the current density of welding surface decreases more slowly, the surface roughness of the solder joint is better, and the qualified rate of the solder joint is higher. The application test and cost analysis of step-up mechanism were carried out in two new models of A platform and M platform. The application test shows that the qualified rate of solder joint is increased by 0.52% and the welding spot quality attenuation caused by the increasing size of electrode end face is eliminated, and the number of spot welding electrode is increased from 4000 to 6000, and the cost of electrode cap and manual replacement of electrode cap are saved, about ￥2.04 million/a.