Abstract: Based on the overlap joint of base plate and lamp shell of LED fish lamp, a three-dimensional thermal-dynamic coupling finite element model was established. Welding software of SYSWELD was used to simulate and analyze the longitudinal residual stress distribution in 316L austenitic stainless steel sheet weld assembly under different welding conditions. The effects of preheating temperature and welding sequence on distribution of longitudinal residual stress were studied, and the simulated results were compared with the experimental results. The results show that preheating can reduce the longitudinal residual stress of weld assembly effectively;longitudinal residual stress decreased with the increase of preheating temperature, but the welding sequence had no significant influence on longitudinal residual stress. The simulation results coincided with experimental results, verifying the accuracy of the model.