Forty-nine species of plants,belonging to 15 families and 38genera,were identified in the middle reaches of the Tarim River in Xinjiang Wei Autonomous Region.The floristic constitution,geographical elements of families,genera of seed plants and species diversity were analyzed in this area.The results show that the flora had highly diverse geographical characteristics.Flora dominance was apparent as many single famili-es and single-genera existed.Most of the flora was strongly xeromorphic and antique.The flora dominated by temperate species,indicating that the flora characteristics of the middle reaches of the Tarim River agreed well with that of the North Temperate zone and old Mediterranean Sea.The percentage of endemic species was low,and rare and endangered plants were scarce.According to species diversity index of different habitats with various forest ages,water was the main factor affecting species diversity.