Theoretical calculations were combined with experiments to explore the photoelectric catalytic performance of MSe2/SnO2 (M = Mo, W) nanocomposites. The electronic structures of the composites were studied by density functional theory(DFT) calculation. Compared with SnO2 material (1.070 eV), the band gap values of MSe2/SnO2 (M = Mo, W) nanocomposites were significantly reduced to 0.133 and 0.008 eV, respectively. Population analysis suggested that the charges transferred between upper MSe2 (M = Mo, W) and underlying SnO2, which could improve the photoelectric catalytic performance of SnO2 materials. Thus, the MSe2/SnO2 (M = Mo, W) nanocomposites were synthesized by hydrothermal method and characterized by XRD. Electrodeposition was conducted to prepare the corresponding electrodes with Fluorine-doped Tin Oxide (FTO) conductive glass to test the photoelectric catalytic performance. The experimental results showed that the photocurrents of the MSe2/SnO2 (M = Mo, W) nanocomposites were 4.8 and 3.0 mu A/cm(2), respectively, and the electrochemical impedance was both smaller than that of SnO2 material. Therefore, the MSe2/SnO2 (M = Mo, W) nanocomposites are good photoelectric catalytic materials.