The endangered species,Urophysa rockii Ulbr.(Ranunculaceae),is endemic to China,with only approximately 2000 individuals confined in the upper reaches of the Fujiang River in Jiangyou City.ISSR PCR (14 primers) was used to assess the genetic variability within and among four extant populations of this species.(1)The results revealed a high level of genetic diversity of U.rockii at species level:percentage of polymorphic loci PPB=97.86%;Nei’s gene diversity (H) 0.306 9;Shannon’s information index (H_sp) 0.466 3.However,there existed little lower genetic variation at population level:PPB=63.22%,H=0.196 2,and Shannon’s information index (H_pop)=0.271 1.(2)A low level of genetic differentiation among populations was detected in U.rockii (0.341 2,0.295 2 and 0.42 for AMOVE,Nei’s genetic coefficient of differentiation (G_st) and Shannon’s diversity index),which may result from out-breeding.(3)There was a significant correlation between genetic and geographic distance among the populations studied.The results indicated that the influence of human activity and habitat fragment may play a prominent role in creating this species’ current endangered status.Based on these results,strategies are proposed for the genetic conservation and management of U.rockii.