The growth of aluminum oxide films depends on the ratio of dissolution and growth rates of the films. Generally, the concentration of the aluminum oxide solution increases, and the dissolution rate of the oxide film also increases. Conversely, as the concentration of the solution decreases, the dissolution rate also decreases. When the oxidation begins, the growth rate of the oxide film is greater in the concentrated solution than in the dilute solution. However, with the extension of the hour, the growth rate in the concentrated solution is lower than that in the dilute solution. Therefore, it is necessary to select the concentration of the solution according to the requirements of the aluminum oxide film. For example, when the concentration of the solution is high, the growth rate of the film is large at the beginning of aluminum oxidation, and the porosity is high, and the dyeing is simplified. However, the membrane hardness, wear resistance and other functions are poor. The oxide film obtained in the dilute solution, wear safety, good reflective, but the low porosity. Only suitable for dyeing various light pale colors. The practice of production proves that for the aluminum oxide film with strong adsorption capacity and elasticity, the concentration of sulfuric acid should be 18%-20%. If the need for wear-resistant decorative oxide film, the choice of sulfuric acid concentration of 16% -17% is more appropriate.