To enhance the welding quality of vehicle power battery pole ears, a nonlinear transient thermo-structural coupling analysis model was developed for 1050/6061 heterogeneous aluminum alloy sheets using the ANSYS simulation platform. The Gaussian surface heat source was applied using APDL language, and the temperature and stress fields of laser deep penetration welding were simulated under specified process parameters. The simulated molten pool shape and size were compared with experimental results, showing good agreement and reliability. The rapid heating and cooling of the laser beam resulted in a large temperature gradient near the heat source and dense isotherms. Stress concentration at the weld center was identified as the main cause of small cracks and other defects in the welded joint, suggesting the need for annealing treatment to reduce equivalent residual stress after welding.