Abstract: Hard anodization technology was exploited with mixed acid of sulfuric acid and oxalic acid for LC9 aluminum alloys.The influence of technology factors such as current density, temperature and sulfuric acid concentration on thickness and microhardness of oxidation film were discussed, and optimal anodization technology was established.The influence mechanism of technology factors on thickness and microhardness of oxidation film was analyzed.Furthermore, microstructure was observed by means of OM and SEM.The results show that oxidation film is even and compact, but crack and pinhole occurs on surface of oxidation film, which is resulted from brittlenes film, dissolution of alloy phase intermetallic compounds and disfigurement of oxidation film.