Based on the data collected from four seasonal surveys in 2011 in Haizhou Bay and adjacent waters, community structure of phytoplankton was studied and their relationships with environmental factors were evaluated by canonical correlation analysis (CCA). A total of 113 phytoplankton species belonging to 3 phyla and 44 genera were collected, among which Bacillariophyta species were the most abundant species, which included 39 genera and 99 species, accounting for 87.6%  of total taxa, followed by Pyrrophyta, which included 4 genera and 13 species, accounting for 11.5 percent of total taxa. And the least abundant species were Chrysophyta species, which had only 1 species belonging to 1 genus.Among these dominant species, Coscinodiscus and Chaetoceros were the dominant groups in Bacillariophyta, while Ceratium was the dominant group in Dinophyta, and the dominant species were Meuniera membranacea, Coscinodiscus subtilis var. subtilis, Eucampia zodiacus and Bacillaria paxillifera. There were obvious seasonal variations in the species composition and predominant species. The abundances of phytoplankton in all the stations ranged from 0.08×10⁵ cells·m^-3 to 108.48×10⁵ cells·m^-3 in Haizhou Bay. The average annual density of phytoplankton was 10.71×10⁵ cells·m^-3, being the highest in autumn (29.08×10⁵ cells·m^-3) and the lowest in summer (1.69×10⁵ cells·m^-3). The Shannon index, Pielou index and Margalef index of the phytoplankton community were higher in summer and autumn than in winter and spring. CCA suggested that the main factors affecting the phytoplankton community were sea surface temperature (SST), followed by nutrients (NO₃^--N, PO₄^3--P, SiO₃^2--Si) and dissolved oxygen (DO). The abundances and distribution of some dominant species were closely related with these main factors.