In the sodium silicate electrolyte system, the uniform ceramic films formed on AZ91D magnesium alloys were obtained by the pulse power when the current density is 40mA/cm2. The morphology, phase composition, anticorrosion and abrasion resistance behaviors in corrosive medium were studied scanning electron microscopy (SEM). The results show that Micro-arc oxidation film is of double-layer structure (loose layer and compact layer), uniform surface and local cracks. Micro-arc oxidation treatment enhanced the anticorrosion of magnesium alloy. The corrosion potential of micro-arc oxidation film is more increased by 94mV than that of the magnesium alloy substrate. The abrasion of the film will be reduced in corroding medium.