Abstract: The energy system of the Space Station Module is a photovoltaic system. Owing to the shadow produced by the section body and other solar arrays, the power generation capacity of the solar arrays would be affected. The paper sets up a solar cell circuit model, to be used on the Saber simulation platform.With the simulation, the relationship between the number of the shaded cells in a cell circuit and the power output is obtained. The shadow based on each cell circuit is calculated with the MatLab, together with the power loss rate caused by the shadow in the autonomous flight phase. The calculation result indicates that the relative error is greater than 5% between the power loss rate and the average blocking rate, the latter is recognized equal to the power loss rate in the traditional calculation method, so that the estimated impact factor of the shadow on the power generation capacity is small. Whereas the proposed method provides a higher precision, which is most applicable when the number of shaded cells is small.