Objective To study the growth and characteristics of hard anodic oxidization film with low sulfuric concentration for aluminum alloy. Methods The hard anodic oxidization of aluminum alloy 6063 was performed in the electrolyte with 3% H₂SO₄ and 18% H₂SO₄ ( mass fraction) , the voltage-time curve and microstructure in the film growth process were analyzed to study the characteristics of the growth of the films. Results In the electrolyte with low sulfuric concentration, the oxidation film grew to " Preferential Growing Mode for Oxidation Film" at the initial stage. At the site of high surface energy defect, the oxidation film core formed continuously and spread out until met and formed the interface; at later stage, the oxidation film grew to " Preferential Growing Mode for Oxidation Film Interface" and was eroded continuously on the thinner oxidation film interface to produce the reverse conveying of Al³⁺ and O^2-, which thickened the oxidation film. Conclusion The growth manner of anodic oxidization film at low sulfuric concentration was obviously different from the traditional one. The film was denser and the thickness, hardness and roughness of the film were greater.