Abstract: Based on the data collected in two surveys in the coastal water of eastern Shishi in spring and autumn 2018, community structure of the net phytoplankton was studied and its relationships with environmental factors were performed by correlation analysis. A total of 145 phytoplankton species belonging to 3 phyla and 51 genera was collected and identified as 122 species of Bacillariophyta, 21 species of Pyrrophyta, 2 species of Cyanophyta. Dominant species in spring included Bacillaria paradoxa, Chaetoceros densus, etc., while the dominated in autumn included Skeletonema costatum, Trichodesmium erythraeum, etc. The phytoplankton cell abundance ranged from 1.81×10⁴ cells/m³ to 410.65×10⁴ cells/m³, and the cell density was higher in spring than in autumn. The average Shannon index was 3.24 in spring and 3.31 in autumn, respectively. According to correlation analysis, temperature, salinity, dissolved inorganic nitrogen and active phosphate were main factors affecting the phytoplankton community.