Abstract: In January and February 2020, 6 sampling sites were selected in Qilu Lake to investigate the community composition of phytoplankton and temporal variation of key physicochemical factors. Combined with biotic and abiotic factors, the succession of phytoplankton community structure in Qilu Lake and the influence of zooplankton on phytoplankton community structure were analyzed, and the dynamic factors of annual succession of phytoplankton community in Qilu Lake were revealed. The results showed that Qilu Lake was a eutrophic water body with high nitrogen and low phosphorus, and its key physicochemical factors presented obvious spatial variations. Comparing with survey data from the last 10 years, the relative abundance and biomass of the phytoplankton community dominated by filamentous cyanobacteria displayed a decreasing trend in Qilu Lake. The phytoplankton community structure showed an obvious seasonal succession. Summer (June–August) is less stable, with cyanobacterial bloom. According to the temporal distribution characteristics of dominant species, it could be divided into the Aphanizomenon flos-aquae and Planktothrix agardhii dominant period. The phytoplankton community was influenced by both key physicochemical factors and zooplanktons.