Abstract: To understand the influence of dams on connectivity of riparian plant communities,three small hydropower plants from up-to-downstream of Modaoxi River were surveyed in September 2008.Plant samples were taken from the small hydropower plants,as well as at the upstream dams,downstream dams and downstream outfalls.Species richness and biodiversity of herbs and shrubs were determined in consecutive 1 m² quadrats and 25 m² quadrats,respectively,along a 50 m long belt transect.157 plant species were recorded on a total sample size of 63 quadrats.The resuit shows that the construction of small hydropower plants has significant impacts on river physical variables(such as current velocity,water depth and substrate types)along the nine sampling locations.The riparian plant community has been more or less affected by the dam construction.The overall species richness and herbs varied significantly in different locations.In contrast,the variability in trees and shrubs is found to be insignificant.Local differences in species diversity are also significant.Hygrophyte species richness has been found to be greater in the upstream and outlets than that of in downstream.The construction of small hydropower plants has disturbed the continuity of riparian plants and has a negative impact on the protection of the plant diversity in the river.