Stannous sulfide (SnS) is a class Ⅳ-Ⅵ layered compound semiconductor material. It’s band gap is very close to the optimal band gap of 1.5 eV for solar cells, and the light absorption coefficient is very large (α>104 cm-1) in the visible light range, so it is a promising material for application. The MoS2/SnS heterojunction solar cells were simulated by using the solar cell simulation software wxAMPS. The influence of SnS absorption layer thickness, doping concentration and defect states on the performance of solar cells were mainly studied. The results show that the optimal thickness of SnS absorption layer is 2 μm, the optimal doping concentration is 1.0×1015 cm-3, and when the concentration of Gaussian defect states is more than 1.0×1015 cm-3, the performance parameters of the cell decrease with the increase of concentration. However, when the concentration of tail defect states exceeds 1.0×1019 cm-3·eV-1, the performance of solar cell decreases. The interface defect states have obvious influence on the solar cell performance, when the concentration exceeds 1.0×1012 cm-2, the open circuit voltage, short circuit current, filling factor and conversion efficiency decrease rapidly. In addition, the optimal conversion efficiency is 24.87%, the open circuit voltage is 0.88 V, and the short circuit current is 33.4 mA/cm2. It can be concluded that MoS2/SnS heterojunction solar cell is a promising photovoltaic device structure.