NOVELTY - A substrate is placed in a multi-source thermal evaporation system. Copper, indium, gallium and selenium sources are supplied. The substrate temperature is increased to 250-450 degrees C and maintained constant. Indium, gallium and selenium are deposition by evaporation. The substrate temperature is increased to 450-650 degrees C, and copper and selenium are deposited. Indium, gallium and selenium are re-deposited. After deposition, the substrate temperature is reduced to obtain a copper-indium-gallium selenide light-absorption thin film layer.    USE - Preparation of copper-indium-gallium selenide light-absorption layer for solar cells (claimed).    ADVANTAGE - The method enables preparation of uniform light-absorption layers, by controlled evaporation, such that an indium-rich phase is generated on the surface of copper-indium-gallium selenide layer. A small amount of sulfur element is introduced on the surface of copper-indium-gallium selenide layer by curing, that is, the copper-indium-gallium selenide layer is heated through light-source irradiation to the surface, and hydrogen sulfide gas is inflated to cure the copper-indium-gallium selenide layer. The method solves the problem of nonuniform distribution of substrate temperature, which is met in the existing contact heating method. The phase structure of the surface of copper-indium-gallium selenide layer is optimized. The recombination of charge carriers in a spatial charge region is reduced and the cell efficiency is improved easily.    DETAILED DESCRIPTION - A substrate is placed in a multi-source thermal evaporation system, which is evacuated to 5x 10-4 Pa. Copper, indium, gallium and selenium sources are respectively supplied at 1100-1250 degrees C, 900-1000 degrees C, 950-1100 degrees C and 200-300 degrees C. The substrate temperature is increased to 250-450 degrees C and maintained constant. Indium, gallium and selenium are deposition by evaporation for 10-15 minutes. After deposition completion, the substrate temperature is increased to 450-650 degrees C, and copper and selenium are deposited for 12-16 minutes. Indium, gallium and selenium are re-deposited for 3-6 minutes. After deposition, the substrate temperature is reduced to room temperature, to obtain a copper-indium-gallium selenide light-absorption thin film layer.