Abstract: Survey of phytoplankton ecology in near-shore areas and aquaculture ponds of Qingduizi Bay were carried out in spring, summer, autumn and winter from 2011 to 2012.In near-shore areas of Qingduizi Bay 61 species of phytoplankton, which belong to 2 phyla, 16 families and 21 genera, were collected, whereas in aquaculture ponds of Qingduizi Bay 53 phytoplankton species belonging to 3 phyla 16 families and 20 genera were collected.Diatoms was the main phytoplankton group of the investigated areas.Noctiluca scintillans、Leptocylindrus minimus and Coscinodiscus wailesii have emerged as the dominant species in summer, autumn and winter.Dominance index(D2) of the near-shore areas are higher than that of the aquaculture ponds, and D2 of the near-shore areas in summer and autumn has reached more than 90%.Near-shore phytoplankton biomass is higher than that of the aquaculture ponds, especially in autumn it is nearly 683 times.Through Shannon-Weaver diversity index and Pielou evenness index analysis, we have found biodiversity and richness of the near-shore areas were better than that of the aquaculture ponds.Compared with other seasons, the phytoplankton community diversity in spring is slightly higher, and it is the lowest in summer.