Abstract: In order to alleviate the tight supply and demand of water resources and guide the management of regional water resources, the optimal allocation model of regional water resources was constructed with the two-way constraints of water supply and water demand to help the comprehensive development of society, economy and ecology. According to the characteristics of the model, NSGA-Ⅲ algorithm was introduced to solve the model to find the Pareto front surface and the optimal solution set. In the face of many feasible Pareto solutions, TOPSIS decision theory was introduced to comprehensively evaluate different solutions, and the tradeoff solution was chosen as the best compromise solution. The model was applied to the Yahekou irrigation area of Nanyang City to verify the optimal allocation of water resources in the short-term and long-term horizontal years under the water inflow frequency of P=75%, and the balance of supply and demand of secondary water resources was analyzed. Compared with the basic scheme, the configuration results show that the annual residual water volume of the compromise scheme increases to 114.976 0 million m~3 at the recent level, and the water resource can be saved by 32.723 8 million m~3.The long-term level of water shortage has changed from 42.792 8 million m~3 to 39.503 0 million m~3, which can save 82.295 8 million m~3 of water. The water-saving effect is obvious, basically in line with the overall planning and water demand of the Yahekou irrigation area.