Dissimilar materials hybrid structures are widely used in lightweight of automobile, and the Al-steel resistance spot welding（RSW） is the core technique in the lightweight of automobile. However, the Al-steel RSW technique is not mature because of the huge differences of the metallurgical properties and thermodynamic properties between Al and steel. The theory and difficulties of Al-steel RSW are described, the research hotspot and status of Al-steel RSW are summarized and the future research directions is discussed.