Abstract: Taking large and medium-sized reservoirs in Shandong Province as the research object, based on SRTM_30 m digital elevation model (DEM) data, vector data of large and medium-sized reservoirs, and measured water level data of reservoirs, using the three-dimensional analysis function of geographic information system software, a reservoir storage estimation model was constructed to calculate the storage capacity of large and medium-sized reservoirs in Shandong Province from 2012 to 2020, and compared and analyzed with the storage capacity of large and medium-sized reservoirs published in the Shandong Provincial Water Resources Bulletin. The model parameters were adjusted according to the analysis results. Use this model to estimate the water storage capacity of large and medium-sized reservoirs in Shandong Province in December 2021, and verify it using data published in the water resources bulletin. The results indicate that the estimated reservoir storage capacity is consistent with the trend of changes in the water resources bulletin data, and the accuracy of the model estimation is high. This method can be used to estimate the reservoir storage capacity at a certain time point.