Abstract: High-speed camera,atomic force microscope and electrochemical workshop were used to investigate discharge regularity during the microarc oxidation process and the corrosion resistance of the coating on Mg-7Li alloy.Results showed that discharge breakdown at the same location continues to the end of the pulse during a pulse period of the power in Na₂SiO₃ solution, while the discharge breakdown occurs at the same location repeatedly with intermittent time up to 160 ms in different pulse periods.The electrode potential of the coating coated alloy increases by 78.1 mV and its corrosion current density decreases by 2 orders of magnitude compared with that of the substrate, which improves the corrosion resistance of Mg-7Li alloy significantly.