With the rapid development of the social economy in the Yangtze Plain, the demand of water intake and allocation in the rivers below water resources zone IV is increasing. Taking Yangxi River-Shuang River area as the research object, the regional water demand prediction results of the study area are put forward according to the monthly water consumption characteristics; On the premise of ensuring the ecological water demand of rivers and lakes, focusing on water conservation and emission reduction, total amount control and optimal comprehensive water use efficiency, build a multi-regional and multi-objective water allocation optimization model to determine the water allocation mechanism below the fourth level of water resources in Yangxi River-Shuanghe River. The results show that: (1) The multi-objective optimal allocation of water volume in regional river network can effectively ensure the red line of total water consumption and the constraints of ecological water demand, and balance the water distribution demand of multiple sub areas between maximizing comprehensive benefits and water conservation and pollution control. (2) The case study shows that the surface water supply of Yangxi River Shuanghe region in normal water years (50%) and low water years (75%) can generally meet the water demand requirements of the near-term (2025) and far-term (2030) level years, but there is water shortage in the near-term and long-term levels in extra low water years (95%), so it is necessary to supplement water from the surrounding rivers; The monthly water distribution analysis shows that the multi-objective optimization scheme fully considers the annual water satisfaction of each sub-region, which better reflects the rigid constraints of water resources on industrial or regional development.