In 2015, the phytoplankton sampling was conducted in Qiandao Lake, and the phytoplankton community structure characteristics, the trend of change and the division of phytoplankton functional groups were studied. Two hundred and one species of phytoplankton were identified. The number of species of Cyanobacteria, Cyanobacteria and diatoms was dominant throughout the year. The average biological density in 2015 was (1285.41 ±448.43)×10⁴ cells/L, and the average biomass was (2.75 ±0.81) mg/L. There were significant differences in biological density and biomass between months (P<0.001). Phytoplankton functional groups S1 and H1 had higher abundance ratio in the four seasons. The B phytoplankton functional groups had a higher proportion in spring and winter, and the J phytoplankton functional groups accounted for higher ratios in spring, summer and autumn. K was higher in spring and autumn, and TC was higher in summer, autumn and winter. M, LO and P phytoplankton functional groups have higher abundance ratio in autumn and summer' and the Y functional group and D functional group are higher in winter only. CCA canonical correspondence analysis revealed the relationship between functional groups and water temperature and nutrients.