In order to solve the poor corrosion resistance of the high rare earth magnesium alloy

the surface of magnesium alloy was treated by micro-arc oxidation to improve its corrosion resistance.For the micro-arc oxidation process

ladder step-down method was employed to control the energy of oxidized film formation at different stages

and the various process parameters were optimized by the orthogonal experiment.With the help of OM（optical microscopy）

XRD（X-ray diffraction）and SEM（scanning electron microscopy）

oxidized film layer thickness

phase constituent and surface morphology of the orthogonal testing samples were analyzed

and the optimized processing parameters were presented in the case of this electrolyte composition:sodium silicate of 15g/L

sodium tetraborate of 30g/L

natrium hydroxydatum of 20g/L

triethanolamine of 15mL/L

nickelous acetate of 0.12g/L and Na-Citrate of5g/L.