For the purpose of effective analysis on rear irradiance of multi-row bifacial photovoltaic module arrays fixed with constant slope angle， a key operation for modifying back side irradiance model of bifacial photovoltaic modules in existence is that a distance of D is divided into n segments with distinguishing shaded and unshaded regions. Subsequently， modified model is achieved by optimizing view factors of diffusion irradiance and reflective irradiance. The simulation and experiments results show that the total radiation of bifacial photovoltaic modules obtained a gain of 18.98% relative to signal photovoltaic modules in the condition of a clear weather， together with the slope angle of 26 °， the height from the ground of 1.5 m， the distance between rows of 4 m， the length of the module of 1.7 m， and the reflectivity of the ground of 30%. Moreover， the irradiance gain error could be controlled only 0.68% in the condition of aforementioned.