Datong River-to-Qinwangchuan Basin Water Diversion Project (hereinafter referred to as the DQ Project) was proposed initially for the purpose of agricultural water supply in the Qinwangchuan Basin at the early stages, but with the development of the construction of new district in Lanzhou, urban domestic water use and industrial water use started to take the largest share of the water supply, which brought the conundrum of reasonable allocation of limited water resources in current research. Regarding to this problem, a multi-objective water resources optimization allocation model was established with the realization of economic, social and ecological benefit maximization as the objective function, the non-negtiveness of water supply, water conveyance capacity, water demand, discharge of drainage system and variables as the constraint condition, according to the sustainable development requirements of the Datong River-to-Qinwangchuan Basin Water Diversion Project water supply area (hereinafter referred to as the DQ water supply area), then the model was solved by genetic algorithm. The results show that in 2025, the water distribution (assurance rate P=50%, P=75%) of different water use departments in the DQ Water Supply Area will be 83.2385×106 and 83.2249×106 m3 of domestic water use, 150.0195×106 and 156.3153×106 m3 of agricultural water use, 111.1100×106 and 111.0000×106 m3 of industrial water use, 9.4688×106 and 9.4702×106 m3 of ecological water use, respectively. The total water distribution of the departments is in balance with the water supply of 423×106 m3 before optimization. In 2030, the water distribution (assurance rate P=50%, P=75%) of different water use departments in this area will be 126.5051×106 and 126.6653×106 m3 of domestic water use, 163.9777×106 and 170.1970×106 m3 of agricultural water use, 204.9800×106 and 205.0800×106 m3 of industrial water use, 9.4800×106 and 9.4888×106 m3 of ecological water use, respectively, and the overall water shortage rate of each department under different assurance rates is 12.27% and 13.38% respectively. From 2025 to 2030, the non-agricultural water use structure of the DQ Water Supply Area would increase greatly, which in turn would cause the decrease of the agricultural water use. In general, the research results can provide some references for the decision-making of the optimal water resources allocation in the DQ Water Supply Area.