Natural occurrence of C4 species, life form, altitude pattern, and infection by the Three Gorges Project (TGP) were studied in the TGP region. 76 species (about 2.5 % of the total 2 685 vascular plant species in the region), in 6 families and 42 genera, were identified with C4 photosynthesis. 91 % of these C4 species belong to Monocotyledoneae, e.g. Cyperaceae (14 species), Gramineae (54 species), and Commelinaceae (1 species). Of these C4 species, Gramineae was the leading C4 family: 54 C4 grass species (71 % of the total C4 species), about 36 % of the total grasses, were identified in the TGP region. 98 % C4 species was found in therophyte (55 %) and hemicryptophyte (43 %). This is consistent with high grass and sedge compositions in the region. Most habitats of more than a half of these C4 species (65 %) will be submerged permanently, but no species will be endangered or extinct, because 95 % C4 species can be found from 500 to 800 m above sea level. The abundance of some C4 species will be dropped due to the reduction of distribution scope. It will take a long-term to explore the effects of the TGP on plants, vegetation, and environment.