In this paper, the copper indium gallium aluminum selenium Cu (InGaAl) Se₂(hereinafter referred to as CIGAS) nanometer powders were prepared by the solvent thermal, and the copper indium gallium aluminum selenium CIGAS film was prepared by directly using the nanometer powders as the evaporation materials. And then the amorphous film was placed in homemade sealing flange with high purity selenium powder to selenide and anneal under vacuum, and conform to the stoichiometric ratio of selenium CIGAS copper indium gallium aluminum selenium film. The structure and composition of CIGAS thin films were determined by X-ray diffraction (XRD), Raman spectroscopy (Raman), scanning electron microscopy (STM) and energy spectrum (ED). The elliptic parameters Ψ(λ) and Δ (λ) of copper indium gallium aluminum selenium CIGAS film were measured using elliptic polarization spectral measurement technique, and then the thin film optical parameters such as refractive index n (λ), extinction coefficient k (λ), absorption coefficient and the film’s light energy gap Eg were obtained , and it was found that the doping of Al significantly increases the light energy ga Eg, and the related physical questions were analyzed too.