Anodic oxidation coatings formed on the surface of magnesium alloys at higher voltage could degrade the mechanical performance of the magnesium alloys material. In order to overcome the shortcoming of mechanical performance reduction, the electrochemical oxidation films were prepared on AZ91D magnesium alloy in Na2SiO3 mainly contained solution and the electrochemical oxidation voltage which was supplied by AC power supply was from 10 V to 110 V. The growth process of the electrochemical oxidation on the surface of AZ91D magnesium alloys was studied. The influence of oxidation voltage and electrochemical oxidation time on the oxidation films was discussed. The microstructure of the electrochemical oxidation films formed at different oxidation voltage and time were analyzed as well. The results show that the corrosion resistance of the electrochemical oxidation films formed at 10 V is as good as that formed at 70~110 V. The growth process of the electrochemical oxidation films formed at 10 V could be summarized under four steps which are grain-like, block-like, integrated insulating and cross-layer films respectively.