The Yongding River is an important water system in the Haihe River Basin, a natural corridor of themain ecological function areas of Beijing-Tianjin-Hebei, and the focus of the coordinateddevelopment of Beijing-Tianjin-Hebei in the ecological field. At present, the contradiction betweenproduction, living and ecological water use in the Yongding River Basin is very prominent. Problemssuch as river cutoff, wetland shrinkage, biodiversity damage, and ecological service function declineare still severe. Therefore, it is of great significance to clarify the ecological water quantity guaranteetarget of Yongding River, analyze the dispatching measures and put forward relevant suggestions inensuring the ecological flow of Yongding River, repairing the structure and function of YongdingRiver water ecosystem, coordinating the optimal allocation of water resources in Yongding RiverBasin and promoting regional sustainable development. Based on natural runoff data, this paperuses Tennant method to calculate the ecological flow of the main control sections of Yongding River,compares the historical measured data of the sections to determine the ecological flow guaranteetarget of Yongding River, and proposes systematic and targeted ecological flow guaranteemeasures from the aspects of ecological flow scheduling, monitoring and early warning, supervisionand assessment.