Abstract: Butt fusion-brazed joint between 5A06 aluminum alloy and ST04Z steel sheets was obtained by low power arc-assisted laser. The welding seam had continuous and beautiful surface appearance. The microstructure and mechanical properties of fusion-brazed butt joint were studied by using SEM, EDS, XRD, tensile testing machine and micro hardness tester. The results show that, compared with a single laser, arc-assisted laser could promote the spreading of liquid aluminum to steel by adding arc heat. The maximum tensile strength of butt joint can reach to 163 MPa, about 74% tensile strength of 5A06 aluminum alloy, which also is 1.3 times of the single laser-welded joint strength. Intermetallic compounds in transition layer of butt joint were mainly composed of rigid Fe₂Al₅ and Fe₄Al₁₃. Tensile failure began in the rigid intermetallic compound layer and ended in tenacious fracture.