The species composition and population size and distribution of mollusca in the middle reaches of Xiang River were studied; and in virtue of diversity analysis software, the species richness indexes (D_MA), and Shannon-Wiener diversity indexes (H′) and evenness indexes (Jsw) of mollusca in fourteen different habitats were analyzed, the system clustering of the mollusca in different habitats were analyzed by Srensen comparability coefficient C . The result of the research showed that there were 53 species of mollusca in the middle reaches of Xiang River ,which belong to 9 families and 20 genera.31 species belonging to 12 genera in 6 families of Gastropoda were found, most of them are representatives of the family Viviparidae. 22 specieses belonging to 8 genera in 3 families of Bivalvia were found, most of them are representatives of the family Unionidae.There were 10 dominance species, 22 companion species, 21 rare species in the middle reaches of Xiang River. The diversity measurements of molluscas in fourteen different habitats showed that values of species richness indexes DMA range from 6.431 9 to 2.318 3; species diversity indexes H′ range from 3.3859 to 2.1834; and evenness indexes Jsw range from 0.94808 to 0.82067. Based on similarity coefficients C ,fourteen habitats can be clustered at the level of 0.5236. The influence of the diversity of the mollusca of the construct of dams on the middle reaches of Xiang River were discussed in the end , and the reason for the highest diversity of mollusca of the collecting site around the Zhuzhou city bridge was analyzed.