Abstract: Projection welding is used for joining auto-door hinge and reinforced plate.To solve problem of uncoaxiality after projection welding,a numerical simulation was presented.Using direct couple method and sequential incremental coupled method,a thermal-electrical-mechanical comprehensive analysis was performed to quantitatively simulate projection welding.Compared with actual experimental measurements,the simulation result was good.It indicated that numerical simulation was a quick and cost-effective method and help to auto-door assembly process optimization.