To investigate the factors affecting the quality of solder joints which would be available for the practical production, an axisym-metric finite element model of the resistance spot welding process simulated by Sysweld finite element software was established for a DP980 steel plate with a thickness of 1 mm. By simulating the formation process of spot welding nuggets, the distribution characteristics of temper-ature field and stress field in the process of spot welding heating and cooling can be studied to determine the nugget diameter and shear strength index. The results showed that the shear force of the spot-welding joint was affected by the structure, and the nugget diameter was non-linear relationship to the shear performance. For the DP980 spot welding joint, the critical nugget diameter of the IF fracture mode to PF fracture mode was 4.695 mm, and the maximum value of nugget diameter and residual stress decreased to different degrees with the in-crease of welding pressure.