Abstract: To explore the seasonal changes of macrozooplankton community structure and the main environmental factors affecting the niche of dominant zooplankton species in the water of the Zhongjieshan islands, the research group conducted four voyages of zooplankton survey in the waters of the Zhongjieshan islands from April 2021 to January 2022. Shannon index and Pianka index were used to analyze the niche breadth and niche overlap of dominant macrozooplankton species in the sea area. Canonical correspondence analysis (CCA) was used to study the main environmental factors of ecological differentiation of dominant species in the sea area. The results showed that there were 11 dominant species of macrozooplankton in the water of the Zhongjieshan islands, and the niche breadth value B_i ranged from 1.80 to 3.46. There was a positive correlation between the dominance index and the niche breadth value. The niche overlap value Q_ik ranged from 0.03 to 0.98. The niche overlap value of the same group was lower, and the niche overlap value between species pairs with predator-prey relationship was higher. There was also a high niche overlap among species belonging to different groups. The results of CCA analysis showed that the environmental factors affecting the ecological differentiation of macrozooplankton in the water of the Zhongjieshan islands included water temperature, inorganic nitrogen, salinity, dissolved oxygen, chemical oxygen demand and phosphate.