Abstract: Dissimilar metals of 5A02 aluminum alloy and galvanized steel were joined with lap joint by gas tungsten arc welding(GTAW) with four filler wires,respectively.The different contents of Si and Cu were added into the weld through different filler metals.It is found that when the Cu content exceeding a certain amount,the intermetallic compounds(IMCs) layer is thicker than 10 μm.When the Cu content is low,the thickness of the IMCs layer decreases with the increase of Si content in the weld.The IMCs layer can be controlled as thin as about 2 μm.Measurements showed that the tensile strength of the aluminum-galvanized steel weld can reach 136 MPa when the Si content is more than 5%,and it is thought that the pores are the main factor to affect the properties of the joint.In addition,more Si addition from the filler metal can improve the microstructure in the zone where the weld and base metal of aluminum alloy joined.