China has a very large number of reservoirs, and the operation of high-density reservoir networks impacts the terrestrial water cycle and the land-atmosphere moisture and energy exchange, which brings challenges to the understanding of hydrological processes and the hydrologic simulation and forecasting. In this regard, this study focuses on the Poyang Lake basin (PLB) and over 1000 reservoirs in the basin, and developed a reservoir network scheme in terms of the reservoir water balance, reservoir release rules, and routing methods with the sectioned two-dimensional diffusion wave equation. The scheme was then fully coupled to the land surface-hydrological model CLHMS through surface water, subsurface water, evapotranspiration and energy balance. Results indicate that the scheme can well capture the reservoir operation, and can enhance the accuracy of streamflow simulation; the reservoirs in the PLB can decrease the runoff by 3.7%—6.0% in the wet season, increase the runoff by 5.9%—12.6% in the dry season, and decrease the multi-year average runoff by 0.6%—1.5% for the Gan, Fu and Xin River. Spatially, reservoirs have a more prominent regulating effect on the streamflow in the middle and northern part of the basin. The newly modified land surface-hydrologic model in this study can provide an analyzing tool and model basis for multidisciplinary research of atmosphere, hydrology and water resources, thereby supporting the sustainable use of water resources in areas under changing environment.