We conducted four investigations on the seasonal variation of zooplankton communities in sea areas around Dachen Island in September (summer) and November (autumn) 2020, January (winter) and April (spring) 2021. A total of 90 zooplankton species (including 15 types of pelagic larvae) were identified, with the maximum of species richness in summer (68 species) and the minimum of species richness in winter (20 species). There were 12 dominant species (Y>0.02) including Sagitta bedoti, Muggiaea atlantica, Furcilia larva, Sagitta enflata, Calyptopis larva, Euchaeta concinna, Diphyes chamissonis, Acartia pacifica, Canthocalanus pauper, Paracalanus aculeatus, Pseudeuphausia sinica, and Calanus sinicus. The seasonal variations were revealed in the abundances and biomass of zooplankton communities, whilst the annual average abundance and biomass were (153.40±214.73) ind/m³ and (411.93±561.76) mg/m³, respectively. The average abundance from highest to lowest was (380.17±296.14) ind/m³ in spring, (135.30±112.59) ind/m³ in summer, (67.88±90.52) ind/m³ in autumn, (25.30±19.11) ind/m³ in winter. The average biomass from highest to lowest was (895.01±802.54) mg/m³ in summer, (623.39±358.73) mg/m³ in spring, (91.08±82.36) mg/m³ in autumn, (45.96±84.95) mg/m³ in winter. The annual average Shannon-Wiener diversity index (H') and Pielou's evenness index (J') were 1.71±0.96 and 0.53±0.20, respectively, which were higher in summer and autumn and lower in winter and spring. Hierarchical cluster analysis revealed that the zooplankton communities could be divided into four groups, including summer group, autumn group, winter group, and spring group. Pearson correlation and RDA analysis showed that water temperature, salinity, and chlorophyll a were main factors related to the distribution and variation of zooplankton communities. In addition, it was noticeable that jellyfish has occurred increasingly and abundantly in summer in sea areas around Dachen Island. Our result will provide useful data for the conservation of biodiversity and sustainable utilization of fishery resources in the marine ecosystem around Dachen Island.