In order to reduce carbon emission, aluminum alloy has been being considered to get light weight car body in automotive industry. But it is difficult to obtain highly reliable joint of aluminum alloy and steel because of the production of hard and brittle intermetallic compounds during the welding process. In this study, aluminum alloys were welded to cold-rolling steel SPCC by resistance spot welding. Effects of welding conditions and alloy element Si, Cu and Mg in aluminum alloy on growth of intermetallic compounds at weld interfacial zones and weld strength of aluminum alloys/SPCC joints were investigated. The intermetallic compound layer was formed of Fe₂Al₅ adhering to the steel and FeAl₃ adhering to aluminum alloy, and the thickness varied with positions along the interface. From EBSD results, the Fe₂Al₅ layer has columnar grains which grew with the 〈001〉 direction perpendicular to the interface of spot welded joint. Diffusion of Si in aluminum alloy happened at the interface, which might inhibit the growth of intermetallic compounds, whereas diffusion of Mg and Cu was not found at the interface by EPMA analysis results. Hardness of intermetallic compound Fe₂Al₅ was affected by the diffusion of Si in aluminum alloy. The tensile shear strength of joint increased with the increasing of welding time, and the maximum tensile shear load was obtained at welding time of 0.134 s and 0.167 s.