Lake Wushan is a highly eutrophic, shallow lake connected to the Yangtze River, and a national wetland park. In order to study phytoplankton structural characteristics in the lake stocked densely with silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis), we conducted a field survey on the phytoplankton community and lake trophic status from September 2017 to August 2018. Trophic status indices (TLI) showed the water quality was between mesotrophic and heavy eutrophic state. A total of 100 phytoplankton species (genera) belonging seven phyla were identified; twenty-three dominant species including nine species of Cyanophyta, eight species of Chlorophyta and both three species of Bacillariophyta and of Cryptophyta were observed. The dominant groups were Cyanophyta in summer and autumn, Chlorophyta and Cryptophyta in winter and spring. The phytoplankton size distribution had a trend biased toward miniaturization. Microcystis sp., Merismopedia tenuissima, Chlorella chlorophylla, Chlorella sp., and Cyclotella sp. were the predominant species in our 2017-2018 annual survey. The peak biomass appeared in June, reaching 34.77 mg/L, and the peak abundance appeared in July, reaching 341.46×10⁶ cells/L. Both of redundancy analyses and linear correlation analyses showed that total phosphorus, temperature and pH were positively correlated with phytoplankton abundance and biomass, and total phosphorus and temperature were also positively correlated with the biomass and abundance of Cyanophyta and the dominant genus. Our results showed that the abundance and biomass of phytoplankton were high, indicating high risks of cyanobacterial water blooms in summer months. Nitrogen was at least as important as phosphorus in limiting phytoplankton production in Wuhan lakes.