In sodium aluminate and sodium hydroxide system, the micro arc oxidation was used to 7 A09 super-high strength aluminum alloy. The influence of oxidation time on ceramic layer thickness, micro hardness, surface and cross-section morphology and phase composition was studied. The results show that, in the condition of the same other parameters constant, with the micro arc oxidation time being 45 minutes, the highest micro hardness of Ceramic layer is 1070 HV0 . 1 , and the ceramic layer mainly consists of γ-Al₂O₃.