Abstract: With the monitoring, the paper demonstrations changes of water environment in Xiangxi River backwater reservoir after the building up of Three Gorges Dam. The industry, residential point source along the river and phosphorus mine non-point source are great of water pollution load. The paper points out that the reduction in DO oxygen along the river were the major factors in fluencing water quality and and backwater reservoir ecosystem. It is predicted that change will lead to phosphorus density increase. To strengthen basins, non-point source pollution control, put the control into practice, build monitoring system online for pollution source, construct pollution treatment project, carry out research on oxygenation and direct-cleaning in lake or river, set up Three Gorges Reservoir water pollution control laws and region regulations, deal with properly the ex-development between resource exploitation and environment prevention, and walk on the sustainable development road are important measures.

Key words: Three Gorges Reservoir, Xiangxi gulf, assessment of water quality, Pollution -preventing administer