Abstract: AZ31B magnesium alloy and 6061 aluminum alloy dissimilar metal riveted part was micro-arc oxidized. The microscopic morphology, phase composition, electrochemical property and hardness of the oxidation film after micro-arc oxidation for different times were studied. The formation process of the oxidation film on the surface of magnesium alloy and aluminum alloy was comparatively analyzed during micro-arc oxidation. The results show that the connected part was integrally wrapped by the oxidation film after micro-arc oxidation for 10 min. The oxidation film connected with the two alloy substrates tightly and consisted of a compact layer and a loose layer. The oxidation film on the surface of magnesium alloy was composed of MgO and a small amount of silicates and fluoride. The oxidation film on the surface of aluminum alloy consisted of Al₂O₃ and a small amount of silicates. The micro-arc oxidation improved the corrosion potential of the magnesium alloy and aluminum alloy, reduced the corrosion potential difference between them and effectively alleviated the occurrence of galvanic corrosion.