Abstract: In the Yuanjiang-Honghe river of China,there are 90 freshwater fishes,belonging to 6 orders,16 families and 65 genura.Dam construction for hydroelectric power in the river will cause hydrological changes and isolate fish's habitat,greatly affecting fishes' migration,feeding and breeding.In order to reduce these influences,some suggestions are put forward,including establishing artificial-breeding station and conservative reserve.