Inter-basin water diversion reallocates water resources by changing their spatio-temporal distribution characteristics between basins. This can effectively relieve water supply and demand conflicts in regions with water resource reserves shortages. However, building inter-basin water diversion projects obviously reduces the inflow from upstream, leading to increasingly conspicuous conflicts between water diversion outside a basin and water utilization inside the basin. To relieve this conflict and explore the optimal scheme of water resource allocation across river basins, this paper chooses the Middle Route Project of the South-to-North Water Diversion Project on the Hanjiang River as a case study. A water supply scheduling model of Danjiangkou Reservoir is built using an integrated inter-basin diversion draw water reservoir regulation (IDR) model to balance multiple conflicting water demands. In the IDR model there are two types of objective sets: aggregate indicators and process matching degree functions. Moreover, six evaluation indexes are selected to analyze the water resource allocation effect of the optimal scheme. The simulation results indicate that the proposed IDR model in this paper is practicable and efficient for water resource allocation across river basins.