In order to understand the relationship between zooplankton species in the Zhoushan waters and the impact of environmental factor changes on the niche differentiation of dominant species, according to the survey data of zooplankton in the Zhoushan waters in the summer of 2019 and 2020, the dominance index was used to judge the dominant species of zooplankton in this sea area. The Shannon formula and the Pianka formula were used to analyze the niche breadth and niche overlap index of the dominant zooplankton species, and the redundancy analysis (RDA) method was used to explore the main environmental factors affecting the niche differentiation of the dominant zooplankton species in the Zhoushan waters for two years. The results showed that the replacement rate of dominant zooplankton species in the Zhoushan waters was 66.67% in 2019 and 2020. According to the niche width value of the dominant species of zooplankton in the offshore Zhoushan waters, they could be divided into broad niche species, medium niche species, and narrow niche species. They accounted for 66.67% and 60.00% of the dominant species of zooplankton in 2019 and 2020, indicating that the broad niche species were the main components of the dominant species of zooplankton in the coastal waters of Zhoushan. The niche overlap index of the dominant zooplankton species ranged from 0.11 to 0.79 in 2019, and the range of the niche overlap index in 2020 was from 0 to 0.98. RDA analysis showed that the niche differentiation of zooplankton dominant species in 2019 was mainly affected by SiO₃-Si concentration, COD, temperature and Chl a concentration, and the niche differentiation of zooplankton dominant species in 2020 was mainly affected by SiO₃-Si concentration and DO concentration. This study is expected to further understand the interspecific relationships of zooplankton communities in the Zhoushan waters, and provide a data basis and scientific basis for studies such as elaborating the adaptation mechanism of zooplankton to environmental changes.