Abstract: Using mean daily discharge data from 1980 to 2015, effects of the Three Gorges Dam on hydrological situation of the Three Outlets were measured based on indicators of hydrologic alteration. Except for a slight increase in Xinjiangkou station and Mituoshi station from January to March, mean monthly flow showed a significant downward trend in the five hydrological stations of Three Outlets, and decreased more in flood season. The maximum daily flow showed an significant downward trend for all hydrological stations in the past decades, but the trend was relatively stable after 2003. Number of days for Shadaoguan station and Guanjiapu station draught-up increased significantly, and the rate of flow change was obviously reduced for all hydrological stations. Hydrologic regime change for the Three Outlets was influenced by its own channel evolution, runoff reduction and runoff process change of the Yangtze River, had some negative effects on the Four Major Chinese Carp populations and the Carex meadow development of Dongting Lake.