In view of the difference of topographic index and water storage capacity in different scales, a scale correction method for water storage capacity is proposed based on the raster topography of the basin. Using the topographic index as an auxiliary factor, two variables that determine the topographic index, namely the upslope catchment area and slope, were respectively scale corrected by introducing the resolution factor and fractal theory; Then, the storage capacity of each scale grid under the corrected topographic index was calculated according to the correlation between the topographic index and the storage capacity. The experiment results showed that the corrected storage capacity of each scale tended to the respective storage capacity of target scale, and the calculated storage capacity area distribution curves approached the target curve. Considering terrain factors, the proposed correction method can not only effectively reduce the influence of grid scale on the calculation of topographic index and water storage capacity, but also greatly reduce the calculation workload and improve the calculation efficiency.