Abstract: The typical defects in anodic oxide film on surface of aluminum alloy were introduced through concrete examples. The cause of various defects was analyzed by macroscopic observation and metallographic examination. The results show that the defects in anodic oxide film on aluminum alloy surface is related to the quality of surface processing,inhomogeneity of aluminum alloy matrix microstructure and the abnormal change of grain size. When the grain size of aluminium alloy is uniform and less than 120 μm, the oxide film has good quality and uniform thickness, and when the grain size is larger than 180 μm, the formation of anodic oxide film is unfavorable.