Abstract: The welding-brazing tests of DC51D+Z zinc-coated steel and 7075 aluminium alloy were carried out by using CMT welding-brazing process. The effects of process parameters on the growth of the interfacial compounds and mechanical properties of the joints were studied by using optical microscope, SEM, EDS and the tensile tester. The spreading behavior of the brazing material on the galvanized steel and the inrterfacial metallurgical reaction mechanism were analyzed and discussed. The results show that the intermetallic compound layer of Fe₂Al₅ and FeAl₃ phases with a thickness of 5-8 μm is formed at the aluminum-iron interface. The galvanized layer on the surface of the steel plate forms a "instantaneous liquid film" under arc heating conditions, which dramatically changes the wetting condition of the filler metal. With the increase of the wire feeding velocity, the maximum tensile force of the joint increases firstly and then decreases. And when the wire feeding velocity is 5 m/min, the average tensile force reaches the maximum value of 2850 N, the joint efficiency is 86.9%.