Abstract: Based on the daily streamflow data of Chenglingji station from 1960 to 2016, two eco-flow metrics, ecosurplus and ecodeficit, were used to evaluate the changes in streamflow and their related ecological effects at the outlet of Dongting Lake. Both annual and seasonal eco-flow metrics were analyzed and the ecosystem influences were also discussed. The results indicated that the average annual ecosurplus and ecodeficit fell in the range of 0-0.39 and 0-0.47, respectively, and the annual ecodeficit had a more frequent fluctuation than the annual ecosurplus. Changes of seasonal eco-flow metrics differed greatly. Ecosurplus had frequent fluctuations in spring and winter, while had no significant fluctuations in summer and autumn. Seasonal ecodeficit showed an increased trend in all seasons except for winter, and were higher than the values of seasonal ecosurplus. The total seasonal ecochange increased during the whole period, and became more discrete during the post-impact period, which indicated a severely disturbance on the ecosystem. Climate change and human activities are two main factors of the eco-flow alteration at the outlet of Dongting Lake. Furthermore, precipitation had greater impact on ecodeficit. Human activities may lead to a large alteration of seasonal eco-flow metrics, through reducing high flow and increasing low flow. According to the four basic principles of flow regimes and ecosystems, Streamflow of Dongting Lake outlet had a close relationship with the ecosystems, and streamflow alteration had negative impacts on the ecosystems.