Abstract: In order to obtain the excellent composite coating on magnesium alloy, double aluminum wires as two electrodes were automatically fed to create electric arc, the melting aluminum drops were sprayed on the AZ91D magnesium alloy surface by compressed air, and then the Mg-Al composite coating was formed.The optimum processing parameters were found by selecting different voltages and air pressure to carry on the spray experiments and analyzing the influence of the parameters on the coating structure performance.The characteristics of the coating microstructure and interface were researched by using the modern analysis methods, and the coating corrosion resistance was analyzed by test the coating electrode potential and the salt-spray experiment.The results indicate that certain voltage and air pressure can cause the coating to be compact.There is the newborn microstructure in the interface.The dual-structures of nano-scale crystal beam and micron-scale lamellar under 50 nm appear in the coating.The corrosion resistance of the coating surpasses that of the magnesium alloy matrix obviously.