Abstract: In order to solve the problems of low quality of the oxide film and easy peeling off of the sealed organic film in the traditional adsorption method of aluminum oxide film, anhydrous ethanol was added into the electrolyte to obtain a smooth and flat aluminum oxide film with a pore size of 50-60 nm, a thickness of 1 μm, and orderly pores. Then a SiO₂ sol-gel with a particle size of 40-50 nm was synthesized. The particle size of the sol matches the pore size of the aluminum oxide film, and the colloidal particles are easily adsorbed by the inner wall of the hole. Under the condition of heating, a composite Al₂O₃-SiO₂ structure can be formed on the surface of the pores to completely seal the aluminum oxide film. The SiO₂ sol-gel prepared by this work is very pure, and there is no introduction of basic catalyst in the whole process, which will not corrode the structure of aluminum oxide film. Finally, the stability and uniformity of the radioactive source were tested. The experimental results show that the radioactive source has good stability and uniformity.