Abstract: For aluminum and steel dissimilar metal welding defects, low efficiency and other issues, proposed a surfacing-stir friction composite welding method, that is, bypass shunt arc welding on the steel plate first, and then using stir friction welding for aluminum alloy surfacing layer and aluminum alloy base material lap welding, get in the aluminum-aluminum interface showing typical stir friction welding “onion ring” Combined aluminium-aluminium-steel composite transition joint. The results show that stir friction welding can effectively eliminate the defects such as porosity in the aluminium alloy deposit layer and achieve the thinning of the metal interface layer. EDS scanning of the aluminium-steel bonding interface shows that the dendritic Fe phase diffusion and the mesh-like inhomogeneous Si phase diffusion can be observed on the aluminium alloy side of the pile. The main components of the joint are Al₅Fe₂Zn_0.4 and Al₇Fe₃Si_0.3 when combined with XRD (X-ray diffraction) analysis. The tensile joint fractured at the base material and reached 100% of the strength of the aluminium alloy base material, meeting the mechanical specifications for the joint application.