The invention relates to a CZTSSe thin-film solar cell with an upper conversion layer and a manufacturing method of the CZTSSe thin-film solar cell. The CZTSSe thin-film solar cell comprises a substrate, a back electrode, a photovoltaic conversion layer, a buffer layer, a window layer, an antireflection layer and an upper electrode, wherein the back electrode is formed on the substrate and deposited according to a magnetron sputtering method, the photovoltaic conversion layer is a CZTSSe thin film, the buffer layer is a cadmium sulfide thin film and is formed on the photovoltaic conversion layer, the window layer is formed on the buffer layer, the antireflection layer is an MgF2 thin film and is formed on the window layer, the upper electrode is made of grid Ni-Al alloy and formed on the antireflection layer, and the upper conversion layer is arranged between the back electrode and the photovoltaic conversion layer. The CZTSSe thin-film solar cell with the upper conversion layer and the manufacturing method of the CZTSSe thin-film solar cell have the advantages that influences of solar heat radiation on the service life of the cell are avoided; according to the method, operation is simple and convenient, manufacturing cost is low, safety and environment friendliness are achieved, and toxicity is avoided; process steps are good in controllability, the upper conversion layer and the photovoltaic conversion layer thin film which are large in grain size, compact and good in photoelectric performance are easily made, and mass production is easy.