The dissimilar welding between aluminum alloys and ultra-high strength steels (UHSS) can realize the structural lightweighting in the manufacturing of vehicle bodies. However, brittle Al–Fe intermetallic compounds (IMCs) are easily formed during welding, limit the industrial application of Al/steel hybrid structure. In this paper, solid rivet resistance riveting welding (RRW) is adopted to join AA6061-T6 aluminum alloy to CR1180T UHSS. This method employs a solid steel rivet to pierce the aluminum alloy workpiece under a piercing current, then a welding current is conducted to weld the rivet to the steel sheet. The influence of rivet leg height, rivet diameter, taper of rivet leg and volume ratio of rivet cap to rivet leg on the joint performance of RRW Al/steel are investigated. The results show that a rivet with small dimension will make it difficult to form effective piercing and welding, and a rivet with too large dimension will increase the difficulty of piercing and welding. With suitable design of rivet dimensions and selection of piercing and welding parameters, the maximum average tensile-shear force of RRW joint reaches 10.8 kN.