【Objective】 To construct an optimal water resources allocation model.【Method】This study chose the water resources of the Yellow River for Gansu Province as the research object. The optimal technique of water resources management decision support system was used to construct the model of optimal allocation of water resources through years of water supply and demand balance analysis.【Result and conclusion】Model calculation results showed that in the 2020 and forward 2030 time period, water resources allocation would be 5.275 billion cubic meter and 6.452 billion cubic meter respectively, including a reduction in agricultural water for 280 million cubic meter and 70 million cubic meter compared to their last decade’s respectively, and other industry water consumption would increase to some extent. This scheme can meet region’s socioeconomic and ecoenvironmental development demands for water resources according to the prediction.