Al films were prepared on quartz substrates by thermal evaporation. The effects of annealing in air on structure and optical and electrical properties have been studied. It is found that the annealing in air will affect on structure and morphology of the films, which results in the difference in the optical and electrical properties. The as-deposited film is amorphous, the films annealed at 200 and 400 degrees C are polycrystalline. After annealed at 600 degrees C, the film was oxidized and changed to porous gamma-Al2O3. The film annealed at 200 degrees C has the maximum reflectance and at 400 degrees C has the minimum resistivity in all samples. While for the film annealed at 600 degrees C, the resistivity is close to be infinite, the reflectance is the minimum at wavelength ranging from 400 to 800 rim in all the samples.