Taking into account defect density in WSe2,interface recombination between ZnO and WSe2,we presented a simulation study of ZnO/crystalline WSe2 heterojunction (H J) solar cell using wxAMPS simulation software.The optimal conversion efficiency 39.07％ for n-ZnO/p-c-WSe2 HJ solar cell can be realized without considering the impact of defects.High defect density (＞ 1.0 × 1011 cm-2) in c-WSe2 and large trap cross-section (＞ 1.0 × 10-10 cm2) have serious impact on solar cell efficiency.A thin p-WSe2 layer is intentionally inserted between ZnO layer and c-WSe2 to investigate the effect of the interface recombination.The interface properties are very crucial to the performance ofZnO/c-WSe2 HJ solar cell.The affinity of ZnO value range between 3.7 4.5 eV gives the best conversion efficiency.