Abstract: Our field experiment made a thorough investigation of the influences of dam operations on the characteristics of the river water eco-environment, and studied the spatial variation of water quality at different control modes (0 m³/s, 20 m³/s, 40 m³/s and 60 m³/s). We also monitored ecological indicators to allow us to analyze the long-and short-term effects of the dam on the river water eco-environment. The results showed that a flow of 60 m³/s benefitted oxidation and decomposition of water pollutants downstream of the dam, and improved river water self-purification. An increase in disturbance of water flow promoted pollutant transfer from the sediment into the water so that a sudden pollution accident resulting from sediment disturbance downstream of the dam could easily take place. Frequent operations occurring in a relatively short period of time significantly affected the density distribution of plankton. What's more, the long-term effects of dam operations led to the development of a very simple biological community and structure, the water eco-environment deteriorated markedly, and the negative effects on the river upstream of the dam were more serious than downstream. The results of this study are useful in providing reliable information for ecological river restoration and sustainable river basin management.