The invention discloses a copper-indium-gallium-selenium thin-film solar cell. The solar cell comprises a substrate, and a back electrode layer, an absorption layer, a buffer layer, a window layer, atransparent electrode layer and a metal gate electrode layer are sequentially stacked on the surface of the substrate from inside to outside. The solar cell is characterized in that the absorption layer comprises m stacked basic absorption layers; each basic absorption layer comprises a copper indium gallium film layer and a selenium film layer stacked from bottom to top, wherein m is greater thanor equal to 2 and less than or equal to 5; the thickness of the absorption layer is 1-2.5 microns; the thickness of the back electrode layer is 0.3-2 microns; the thickness of the buffer layer is 20to 200 nm; the thickness of the window layer is 20-200 nm; the thickness of the transparent electrode layer is 0.3-2 microns; and the thickness of the metal gate electrode layer is 2-10 microns. The gradient of gallium changes along two directions of the back surface of the absorption layer and the surface of the absorption layer, so that the depth distribution of gallium in a copper-indium-gallium-selenide absorption layer and the increase of the band gap width of the absorption layer are promoted, and the open-circuit voltage and the photoelectric conversion efficiency of the thin-film solarcell are further improved.