A method for fabricating a Cu—In—Ga—Se film solar cell is provided. The method comprises: a) fabricating a molybdenum back electrode on a substrate; b) fabricating a Cu—In—Ga—Se absorbing layer on the back electrode by fractional sputtering in a plurality of sputter chambers; c) performing an annealing; d) fabricating an In2Se3 or ZnS buffer layer on the Cu—In—Ga—Se absorbing layer; e) fabricating an intrinsic zinc oxide high impedance layer on the In2Se3 or ZnS buffer layer; f) fabricating an indium tin oxide film low impedance layer on the intrinsic zinc oxide high impedance layer; g) fabricating an aluminum electrode on the indium tin oxide film low impedance layer.