NOVELTY - Preparing copper indium disulfide thin film comprises (1) depositing copper thin film on the clean molybdenum, titanium, iron, or palladium active metal substrate by chemical plating method; regulating pH; (2) depositing indium thin film on the prepared thin film in step (1) by chemical plating method to obtain copper-indium precursor; regulating pH; and (3) processing the prepared copper-indium precursor for 30-180 minutes at 300-700 degrees C or 10-50 minutes at 50-160 degrees C and then for 30-180 minutes at 300-700 degrees C to obtain copper indium disulfide thin film.    USE - The method is useful for preparing CuInS2 thin film (claimed). The CuInS2 thin film is useful as the absorption layer of the solar energy batteries.    ADVANTAGE - The method is simple; there is no need of vacuum device; the cost is much less than the sputtering method and co-evaporation method; there is no need for electricity and the cost is even much less than the plating; moreover the thin film prepared is average in the surface with little clearances; it completely satisfies the requirements of the product as the absorption layer of the solar energy batteries.    DETAILED DESCRIPTION - Preparing copper indium disulfide (CuInS2) thin film comprises (1) depositing copper thin film on the clean molybdenum, titanium, iron, or palladium active metal substrate by chemical plating method; where the solution preparation of chemical plating copper comprises 0.001-5 mol/l of cupric salt, 0.001-5 mol/l of complexing agent, and 0.001-5 mol/l of reducing agent; and the pH of the solution will is regulated till basic; (2) depositing indium thin film on the prepared thin film in step (1) by chemical plating method to obtain copper-indium precursor; where the solution preparation of indium comprises 0.001-5 mol/l indium salt, 0.001-5 mol/l of complexing agent, and 0.001-5 mol/l of reducing agent; and the pH of the solution is regulated until basic; and (3) processing the prepared copper-indium precursor for 30-180 minutes at 300-700 degrees C or 10-50 minutes at 50-160 degrees C under the protective atmosphere of argon with sulfur or nitrogen, and then for 30-180 minutes at 300-700 degrees C to obtain CuInS2 thin film.