From 2017 to 2020,the biological resources such as fish,plankton and aquatic macrophytes at Hanzhong,Laohekou and Zhongxiang sites in the main stream of Hanjiang River were investigated and analyzed seasonlly. The results showed that 98 species of fishes were collected,among which the economic fish were mainly carp,crucian carp,silver carp,bighead carp,and grass carp,etc. A total of 116 species of phytoplankton belonging to 71 genera,7 phyla were identified,among which 46 species were Chlorophyta,and 12 dominant species were Bacillariophyta. A total of 86 species of zooplankton belonging to 55 genera were detected,among which 48 species were rotifers,and 8 species were dominant,mainly protozoa. There are 29 species of aquatic macrophytes belonging to 24 genera and 16 families. Compared with the monitoring data in the past,there are 38 fewer fish species in the main stream of Hanjiang River,and the main species were rare and small fish,such as Metahomaloptera omeiensis and Glyptothorax sinensis. There were 27 new fish pecies,the total number of fish species decreased,the catch miniaturization was obvious,and the fishery resources declined. The species,density and biomass of phytoplankton increased; the species of zooplankton increased,and the density and biomass increased; and the species of aquatic macrophytes decreased. The above changes are related to the construction of water conservancy projects such as the Middle Route Project of South to North Water Diversion and the cascade development of Hanjiang River,the change of hydrological regime such as the decrease of discharge water,the artificial regulation of runoff,the decrease of discharge water temperature,the slowing down of water flow in some river sections,and the acceleration of water eutrophication. It is suggested that the protection of fishery resources and environment in Hanjiang River should be strengthened through the implementation of pollution control in the river basin,the implementation of artificial proliferation and release,and the management and control of ecological flow.+E100