Abstract: In areas with frequent human activities, water resource development and utilization causes variations in river hydrological regimes, which leads to changes in the water ecosystem.Variations in river hydrological regimes differ from region to region, therefore, it is necessary to consider the characteristics of river hydrological regime changes and assess their impact on local water ecosystems in the regional management of ecological flow for proposing more region-targeted measures.Taking the Lower Hanjiang River, Hanbei River, Tianmen River, Fuhuan River region(Lower Hanjiang River and Hanbei-Tianmen-Fuhuan tributary area)as the research area, the daily average discharge of the long series of six hydrology stations, including Huangzhuang, Shayang, and Xiantao stations in the Lower Hanjiang River, and Geputan, Tianmen and Yingcheng stations in the tributary area, were selected to analyze the abrupt change of runoff, IHA-RVA was used to compare the characteristics of hydrological regime variations before and after the abrupt change of runoff at different stations in the study area.Suggestions were put forward for ecological flow control in the study area based on the ecological significance of these indicators.The results showed that:(1) Runoff abrupt change in the Lower Hanjiang River occurred in 1990,and that of the tributary area occurred in 2010.After the abrupt change, discharge decreased, and the dry period was prolonged.(2) Excessive variation of hydrological indicators before and after the abrupt change of runoff in flood season existed in all six stations in the study area, which might adversely affect the reproduction of aquatic organisms, especially the fish that spawn floating eggs, causing the reduction of aquatic resources.(3) The positive variation of the hydrological indicators of the Lower Hanjiang River was much more than that of the tributary area while the middle to high variations were much less than that of the tributary area, and more IHAs of the tributary area presented a deviation from suitable range than the Lower Hanjiang River.The results are scientifically significant for understanding regional variation characteristics of ecological flow and provide a reference for regional management of ecological flow.