The invention discloses a double-section CIGS solar cell and a preparation method thereof, belongs to the technical field of CIGS solar cells, and solves the problem of poor light/heat/humidity stability of the double-section CIGS solar cell in the prior art. The battery sequentially comprises a back electrode layer, a first absorption layer, a buffer layer, a first transparent electrode layer, atransparent insulating layer, a second transparent electrode layer, a second absorption layer and a third transparent electrode layer, which are stacked on a substrate. The band gap widths of the first absorption layer and the second absorption layer are different. According to the preparation method, the back electrode layer, the first absorption layer, the buffer layer, the first transparent electrode layer, the second transparent electrode layer, the second absorption layer and the third transparent electrode layer are sequentially arranged on the substrate. The double-section CIGS solar cell and the preparation method thereof can be used for solar power generation.