Abstract: In order to reveal the relationship between welding parameters and mechanical properties of welding spot, a FE(Finite Element) model of RSW (Resistance Spot Welding) was founded by using multi-physical fields. Forces of spot weld under car body complicated working conditions were analyzed, the tensile force, shear force and required welding time were taken as the constraint conditions, a new method to optimize welding parameter was proposed as the object of getting the lowest welding energy consumption based on “quality-energy consumption” balance model. The equilibrium advantages of mechanical properties and industrial energy consumption of RSW were obtained. A typical structure of safety belt anchorage was set up to verify the optimization method. Compared with the welding parameters obtained from the traditional method, the optimized welding parameters by the proposed method can not only meet the requirement of mechanical property, but also reduce the energy consumption by 55%, which is of great benefit to automobile factory.