Abstract: Aiming at the welding quality and strength of thin plates with unequal thickness in railway vehicle manufacturing,spot welding process of SUS301 L thin plates with unequal thickness was simulated by special welding software in this paper. Based on the comparison between the simulation results and the experimental results,effects of welding current,electrode pressure and welding time on the equivalent stress after welding were studied. The feasibility of the simulation model was verified by nugget size comparison. The result showed that the distribution of high stress zone after welding expanded with the increase of current and time,the high stress area decreased after welding with the increase of electrode pressure. This research provided process reference for spot welding of SUS301 L thin plates with unequal thickness and it was of great engineering significance in railway vehicle manufacturing.