Abstract: Al-43%Zn-1.6%Si alloy on the Q235 steel surface which was pre-coated Zn was hot-diped by a new process of melt treatment and metal assistant plating.The morphology and phase composition of the coating were analyzed by means of optical microscope,scanning electron microscope and energy dispersive spectroscope.The corrosion resistance and mechanical properties of the hot-diped plate were investigated.The results show that the thickness of the Al-43%Zn-1.6%Si alloy coating prepared with the new hot-diped process was about 50 μm.The microstructure of the coating was dendrite,and the alloy coating was composed of Al-Zn-Si-Fe quaternary phase.The plate had good corrosion resistance in NaCl solution,whose corrosion rate was 1.7×10-2 mg·cm-2·h-1.After hot-diped,the plasticity of the steel increased,and a silverly witheout any bare spots plate with good performance was obtained.