Abstract: The phytoplankton sampling was conducted seasonally in the middle and lower Hanjiang River from July 2017 to May 2018. Community structure and the functional groups of phytoplankton were analyzed and water quality evaluated accroding to the phytoplankton functional group classification. A tatal of 145 phytoplankton species, belonging to 75 genera and 7 phyla, were identified during the study period. The dominant species of phytoplankton were species of Bacillariophyta. The density of phytoplankton ranged from 1.51×105 to 4.33×107 ind/L (7.57×106 ind/L in average). The biomass of phytoplankton ranged from 0.088 7 to 17.259 3 mg/L (4.849 5 mg/L in average). Twenty-three different phytoplankton functional groups were constructed in the middle and lower Hanjiang River, and the relative biomass of two functional groups, namely functional groups P and D, was more than 10%. The water quality was comprehensively evaluated by phytoplankton saprobie indicator, Shannon-wiener index and Qr value. Our results indicated that the water quality in the middle and lower Hanjiang River was slightly-moderately polluted. The water quality in summer was worse than in spring and summer.