In order to realize the lightweight of automobile and ensure its safety coefficient,the joining technology of steel and aluminum dissimilar materials becomes the research focus. Numerical simulation is one of the effective ways to study the mechanism of Al-Steel resistance spot welding（RSW）. The establishment and development of a model for Al-steel RSW is summarized. The research progress of the numerical simulation for Al-steel RSW is introduced from three aspects: formation of nugget,formation of the intermetallic compounds and analysis of other welding parameters change. In addition,the future development space of numerical simulation of Al-Steel RSW is discussed.