Abstract: In order to achieve good automotive joining of aluminum/steel dissimilar metals, the experiments of butt joining aluminum alloy to galvanized steel were carried out by laser deep penetration welding-brazing with a fiber laser. The seam appearance, the intermetallic composition layer as well as the mechanical properties of the joints were analyzed. The results show that a typical deep penetration welding seam is formed on the aluminum alloy side, while a brazed seam is generated on the solid galvanized steel side. There is a thin layer of the intermetallic composition on the interface between the galvanized steel and the brazed seam, which is less than 10μm. The main intermetallic compositions were Al7.2Fe2Si and (Al,Si)13Fe4. The tensile samples were fractured at the heat affected zone of the aluminum alloy. The average tensile strength of the joint is 145MPa. The fracture mode of the joint is ductile fracture.