Abstract:Based on the minimum hydrological runoff value and annual mean flow data of the main tributaries in the region of Yunnan area in the Jinsha River Basin from 1968 to 2017, the evolution characteristics of minimum values were analyzed by linear regression and Mann-Kendall method, and the river ecological base flow were comprehensively analyzed by Tennant method and regional experience, and the protection degree of ecological base flow was evaluated. The results show that, the northeast and northwest areas of the study area are the high value area of the annual minimum value corresponding to the high yield area per 100 km2, and the Dianzhong area is the low value area. The regional differences are significant. The annual minimum runoff value in the northeast region shows a significant fluctuation decreasing trend. The variation trend of Dianzhong area, North Central District and Northwest area is different. On average, only 47 percent years of ecological base flow are guaranteed and 53 percent years hydrological minimum value is lower than ecological base flow in the main tributaries, in which Northeast China and Northwest China have a higher level of security, while central Yunnan has a lower level of security. It is predicted that the northeast region will be affected by natural water inflow and some rivers in the northwest region will be affected by water conservancy and hydropower project dispatch. The pressure of ecological base flow security will gradually increase. In Dianzhong area, except for some of the rivers in Kunming and Qujing, the degree of ecological base flow protection will be gradually improved, most of the other rivers will continue to be in a high pressure state.