Doping is a simple method to modulate the electronic configuration of semiconductor photocatalysts. This study regulated the energy band structure of CdSe nanosheets by Ag doping, which reduced the energy bandwidth of CdSe nanosheets by increasing the carrier density, thereby improving the efficiency of the photocatalytic reduction of uranium by CdSe nanosheets. A 96% removal of U(VI) was achieved by 3% Ag-CdSe nanosheets, which was 1.9 and 1.2 times higher than that of pristine CdSe nanosheets (50%), and 1% Ag-CdSe nanosheets (81%), respectively. Additionally, at pH = 4.0 and a solid−liquid ratio of 0.25, the reduction of uranium by 3% Ag-CdSe nanosheets (765 mg/g) was 2.2 times higher than that of pristine CdSe nanosheets (345.6 mg/g). This study provides a new idea for other efficient photocatalysts designed for uranium reduction.