Abstract: A distribution flow method（DFM） and its ecological flow index（DEFI） and evaluation grade standard（DFGS） are proposed to study the ecological flow of rivers on the basis of Multi-probability density estimation. Taking the Yichang section of the Yangtze River as an example, The proposed DFM compared with traditional calculation method of hydrological ecological flow, method of flow evaluation, and calculation result of fish ecological flow, and the changes in river ecological flow satisfaction rate and ecological index score before and after variation are evaluated. Results show that the DFM considers the intra-and inter-annual variations in natural runoff, thereby reducing the influence of extreme flow and uneven flow distribution during the year. The method can meet the actual runoff demand of river ecosystem, is superior to traditional hydrological method, and presents strong space-time applicability and certain application value.Inter-annual changes in wet, normal, and dry seasons should be considered, and the ecological flow level and ecological flow index scores higher or close to those before the variation should be used as the criteria for water resources and ecological flow management.