The characteristics of the spatial distribution of plankton in the Hangzhou Bay estuary (27°38'- 28°02'N, 120°50'-121°14'E) were investigated in April, 2012. The correlation between the distribution of plankton and eutrophication was studied, and the results were presented in the paper. During the investigation, serious eutrophication prevailed with eutrophication index (E) higher than 1; the growth of phytoplankton was limited by light intensity due to high suspended particulate (SP) in the estuary. High abundance of phytoplankton was observed as light condition improved because of decreasing SP concentration. The distribution pattern of zooplankton was in coincidence with that of phytoplankton. The abundance of zooplankton was significantly correlated with that of phytoplankton, suggesting the limitation of eutrophication and SP on production in the Hangzhou Bay. In spring, the species number and the dominant species number (2 species) were relatively small, and also displayed the characters of high dominance and average abundance of single dominant species and average value relatively of diversity index low (1.78). Though the structure of zooplankton was not very stable, the coincidence in the distribution of zooplankton and phytoplankton indicates the grazing pressure of zooplankton on the growth of phytoplankton. We conclude that the ecosystem in the eutrophication areas of Hangzhou Bay was stabilized in spring.