The impact of the Three Gorges Hydroelectric Project on the plant diversity in the reservoir region was assessed based upon field surveys of the plant species and vegetation surrounding the reservoir area that will be influenced by this project. The reservoir area harbors known higher plants （except Bryophytes） of 190 families, 1012 genera, 3012 species （including 29 sub-species, 286 varieties and 16 forms）. Of which, 37 endemic species can onlyy be found in the reservoir region, 47 species, including 22 endangered species, 20 rare species and 5 threatened species, have been listed in the ＂Plaant Red Data Book of China＇. Vegetation types in the reservoir area, except for those found in the cultivated land, have 89 formations. The coniferous forests are most widely distributed, while broadleaf evergreen forests are only scattered in the central parts of the mountain. The plants belonging to 120 families, 358 genera and 550 species that are at present distributed under the flooded line （185 m） in the reservoir will be affected by the projject, based on their current distributional range from the established database. Moreover, 27 community types in the potentially flooded area will be eliminated from the area as well, since the original habitats of some species will be destroyed after the reservoir is filled with water. Flooding will directly lead to the extinction of species and community types in the reservoir region unless preservation strategies are to be taken. Even if it is assessed solely based on the loss of natural vegetation and the destruction of the habitats that are currently cultivated, the economic loss caused by flooding will be severe.