Abstract: Based on a brief introduction of environmental policy of the World Bank on the hydropower project, this paper summarized respectively the longterm ecoenvironmental monitoring plans and the measures for reducing the side effects caused by the four famous hydropower stations (Egypt's Aswan High Dam, Brazil's Itaipu Dam, China's Ertan Dam and Three Gorges Dam). A hydropower project is of negative or positive impacts on the environment in related regions and the negative impacts of largescale dams as mentioned above are focused on. The Egypt's Aswan High Dam was constructed in 1960s while the ecoenvironmental impact issues were not arose. After its completion, the Egypt's High Dam had been praised as the mainstay of Egyptian economy and vilified as an environmental catastrophe. Longterm ecoenvironmental monitorings have shown that a lot of environmental impacts such as bed erosion had been exaggerated and a few such as traditional brick making industry ignored. The Brizil's Itaipu Project had taken measures to reduce the side effects while under construction, including measures for forest area conservation surrounding the reservoir, biological shelters and nature reserves construction, animal rescue centers etc. China's Ertan Project supported financially by the World Bank had carried out the environmental policy to reduce the side effects. By sharing the experiences of largescale hydrpower projects, a series of measures to protect the environment are being implemented for the ongoing Three Gorges Project, in which the largest ecoenvironmental monitoring network has been set up.

Key words: hydropower project, ecoenvironmental monitoring, Aswan Project, Itaipu Project, Ertan Project, Three Gorges Project