Distributed Watershed Hydrological Models with physical basis usually use the DEM grid as the calculation unit, which can homogenize the terrain information so that the extracted slope is non true value, and the non true value corresponding to different scale grids is significantly different, which leads to significant differences in simulation results based on different scale distributed models. In view of the influence of different resolutions on the simulation results, a normalized expression method of the relationship between grid scale and the extracted watershed slope and the corresponding slope correction method are proposed. The slope correction coefficient which can be used in the calculation formula of model velocity is introduced in the correction method. The results show that the influence of cell size on the simulation results is consistent with that on the extracted watershed slope, and the proposed method can effectively eliminate the influence of grid equalization on the simulation results of distributed hydrological model.