Abstract: 6061 aluminum alloy and Q235 galvanized steel were butt welded by cold metal transition(CMT) brazing. The microstructure and tensile properties of welded joints were studied. The results show that the welded joint surface was well formed. The welded joint was composed of fusion zone, heat-affected zone and interface layer. The fusion zone consisted of α-Al solid solution and aluminum-silicon eutectic structure. The microstructure of heat-affected zone was coarser than that of the parent metal. Intermetallic compound (IMCs) was formed in the interface layer, the layer thickness was about 8 μm, and the layer grew unidirectionally to the melting zone. The hardness of the heat-affected zone on the side of 6061 aluminum alloy base metal was the lowest (42 HV), and the hardness of the IMCs layer was the highest (365 HV). The tensile strength of the welded joint was 161 MPa, which was about 0.69 times as that of 6061 aluminum alloy, and was improved obviously compared with lap joints.