NOVELTY - Preparing copper indium gallium selenide thin film material, comprises: preparing precursor solution by dissolving nitrate or chlorate of copper, indium and gallium in alcohol, dissolving highly pure selenide powder in amine, mixing, adding to viscosity adjusting agent; using regular film forming technology e.g. spin coating method to prepare precursor thin film on substrate; placing precursor thin film in annealing furnace for thermal processing; and placing precursor thin film in selenylation furnace, using pure selenide powder as selenide source and performing selenylation.    USE - The method is useful for preparing copper indium gallium selenide thin film material.    ADVANTAGE - The method is simple, economical, environment- friendly, and easy to prepare large-area high-quality copper indium gallium selenide thin film.    DETAILED DESCRIPTION - Preparing copper indium gallium selenide thin film material, comprises: (i) preparing precursor solution, where the solute is nitrate or chlorate of copper, indium and gallium, and a highly pure selenide powder with a purity of 99.99%, with a ratio of copper, indium, gallium and selenium as 1:0.7-1.4:0-0.5:0-0.02, and the solvents are alcohol and amine, where the mass ratio of the viscosity adjusting agent and solvent is 1:10-20, dissolving the nitrate or chlorate of copper, indium and gallium in alcohol, dissolving highly pure selenide powder (0-0.06 M) in amine, mixing the solution, adding to the viscosity adjusting agent, stirring for 8-14 hours at room temperature to form the stable precursor solution, then adding or reducing the amount of alcohol or amine to control the concentration of copper in precursor solution to 0.1-0.5 M; (ii) preparing precursor thin film at room temperature and normal pressure by using the regular film forming technology e.g. spin coating method, lifting method or scraping method to prepare the precursor thin film on the substrate, where the thickness of the thin film is determined by the requirement of the device; (iii) placing the precursor thin film in the annealing furnace for thermal processing for 5-20 minutes at 200-300 degrees C; and (iv) placing the precursor thin film in a selenylation furnace, using the highly pure selenide powder with a purity of 99.99% as selenide source, and using the solid source selenylation technology to conduct selenylation process for 15-40 minutes at 400-500 degrees C to form the copper indium gallium selenide thin film of formula CuIn(1-x)GaxSe2.