Abstract: In order to explore the succession of phytoplankton functional groups and the status of aquatic ecology in the aqueducturous section of Huaihong River, eight quarterly surveys were carried out on the Xinhuihe section of Huaihong River in 2019 and 2020. The evolution trend of phytoplankton functional groups and the main environmental factors were investigated by using the functional group division method and redundancy analysis (RDA). The comprehensive nutritional status index, diversity index and Q_r index were used to evaluate the water environment. The results show that during the survey period, there were 136 species in 70 genera and 8 phyla in Huaihong River. Chlorophyta accounted for the highest number of species (52.21%), followed by cyanobacteria (19.12%) and diatoms (13.24%). The mean quarterly variation of phytoplankton abundance ranged from 1.60×10⁶ to 3.61×10⁷ L^-1, with an average of (8.99±3.84×10⁶) L^-1, and the mean quarterly variation of biomass ranged from 0.59 to 6.07 mg·L^-1. The mean value was (2.48±0.35) mg·L^-1. The dominant species of phytoplankton were Chroomonas acuta, Cryptomonas erosa, Cryptocryptophyta acuminatum, Microcystis and so on. A total of 25 functional groups were divided for Huaihong River, among which 9 were dominant functional groups. The seasonal succession characteristic of dominant functional groups from 2019 to 2020 was as follows: B/X2/Y (spring) →M/J/Y (summer) →B/P/Y (autumn) →B/X2/Y (winter) →B/X2/Y (spring) →J/S1/S2/Y (summer) →B/P/J/Y (autumn) →B/E/Y (winter). The dominant functional groups B and Y indicated that the water state of Huaihong River was mesotrophic to eutrophic still water. RDA results show that temperature, nitrogen and phosphorus nutrients and pH were the main environmental factors affecting the evolution of dominant functional groups in Huaihong River. Q_r index indicates that water quality of the Xinhuihe section of Huaihong River was "good-medium", which was similar to the evaluation result of comprehensive nutrient status index. Compared with diversity index, Q_r index is more suitable for water ecological evaluation of the aqueductary section of Huaihong River.