Abstract: Based on the data collected from Akashiwo sanguinea-dominated algal blooms occurred in the coastal waters of southern Zhejiang province, in mid-June 2016, the species composition and abundance, dominant species, diversity indices of plankton community between algal bloom and non-bloom areas were compared, and the relationships of biodiversity to environmental factors were analyzed. A total of 22 phytoplankton and 20 zooplankton species were identified. The average abundance of phytoplankton in the bloom area was significantly higher than that in the non-bloom area. No significant difference in the average abundance and biomass of zooplankton was found between the bloom and non-bloom areas. The average evenness index of phytoplankton in the non-bloom area was significantly higher than that in the bloom area. However, and no significant difference in other biodiversity indices of zooplankton existed between the bloom and non-bloom areas. In addition, the number of copepod species and their abundances in the bloom area were significantly less than those in the non-bloom area. The results of principal component analysis for the dominant species and environmental variables showed that A. sanguinea abundance positively correlated with nutrients in the non-blooms area, but negatively correlated with the ones in the blooms area. The total zooplankton abundance was positively correlated with Ceratium furca both in the bloom and non-bloom areas, but negatively correlated with the abundance of Gonyaulax spinifera, a toxic dinoflagellate. These results indicate that the Akashiwo sanguinea-dominated algal blooms can significantly change the community structure of plankton.