Applying the technology of micro plasma oxidation to improve the surface of 7075 aluminum alloy in sodium aluminate solution, effects of anodic current density(Ja)and the ratio of cathodic current density(Jc)to anodic current density on thickness and hardness, surface and cross-section morphology as well as phase composition were studied. The results show that, the thickness and hardness as well as surface and cross-section morphology are closely related to Ja and the ratio of Jc/Ja. Better comprehensive property of ceramic coatings is obtained while Ja is 10A/dm2 and ratio of Jc/Ja was 0.7.