The boehmite sol is prepared with cheap inorganic salt Al(NO3)3 and NH3H2O. The anodized aluminum alloy was sealed with the boehmite sol. Influences of concentration of Al3+, pH and temperature of sol on the properties of sol and the sealed film were studied. The results shows that the viscosity of sol increases and the stability becomes lower with the increase of Al3+concentration and pH of sol. The viscosities of sol become lower with the rises of its temperature. The thickness of anodized film increases when sealed with boehmite sol. The thickness value of sealed film increases with the increase of the sol viscosity. The properties of sealed film are better while the color of sol is azury. The corrosion resistance of sealed film was enhanced with the pH rising from 5.5 to 7 at the same concentrate and temperature of sol. The corrosion resistance in acidic solution is improved remarkably for sol sealed film as the sol temperature rises up to 60°C. The time of changing colour for sol sealing film is longer than that of the film sealed by distilled water.