For silicon heterojunction solar cell with p-type a-Si:H back surface field, the effects of substrate resistivity on the performance of solar cell with different defect densities on the front and the rear surfaces of the p-type c-Si wafer are investigated numerically by computer simulation. The results indicate that the optimized resistivity of the substrate (ρop) is related to the interface defect density on the front surface of c-Si wafer (Dit1), and ρopincreases with the increase of Dit1.The value scale of resistivity of substrate is influenced greatly by the interface defect density on the rear surface of c-Si wafer (Dit2) for ρ>ρop, and the larger the value of Dit2, the smaller will the range of acceptable ρ value be.