A combination of self-pierce riveting and resistance spot welding, which is named resistance rivet-welding, was used to join aluminum alloy sheet and mild steel sheet. To enhance the performance of the joints between aluminum alloy and mild steel, a supplementary plate was used for joining. The effect of welding current on the performance and cross-section geometrical characteristics of resistance rivet-welded joints with and without supplementary plate was compared and analyzed. A reaction layer composed of Fe2Al5 and FeAl3 was formed at the interface between the rivet leg and the aluminum alloy, the mild steel and aluminum alloy in the resistance rivet-welded joint with supplementary plate. The tensile shear load and cross tension load of resistance rivet-welded joint with supplementary plate increased first and then decreased with the increase in welding current, which achieved the maximum value of 7.51 kN and 4.23 kN when the welding current was 6 kA, respectively. The results reveal that the application of supplementary plate in the resistance rivet-welding between the aluminum alloy and mild steel can not only prevent the failure of the rivet cap being pulled out from the upper plate when the joint is loaded, but also improve the tensile shear load and cross tension load of the joint.