The Zhoushan Sea (121.82°-122.35°E, 29.80°-30.22°N) is located along the northeast coast of Zhejiang Province, where the estuaries of the Yangze and Qiantang Rivers converge. The Zhoushan Sea is one of the deepest harbors in China, and it provides the largest marine economic base for the country. However, an increase in oil pollution and eutrophication in the area has been observed in recent years, which poses considerable threat to marine environments and resources. Understanding how oil pollution and eutrophication influence the marine ecological environment in the Zhoushan Sea is fundamental to protecting marine resources. Zooplankton plays a key role in marine food webs, and they are often used as indicator species of both small-, and large-scale nutrient pollution in aquatic ecosystems. However, there is little information available on how environmental factors influence the zooplankton community in the Zhoushan Sea.Our study investigated how environmental factors affect the zooplankton community in different seasons. In 2014, we conducted a summer (July) and autumn (October) survey in the Zhoushan Sea, to measure the abundance, biomass, and temporal and spatial distribution of the zooplankton community. Multidimensional scaling (MDS) and canonical correspondence analysis (CCA) were used to study the zooplankton community. In summer, we documented 64 species in 13 groups, with 6 dominant species: Centropages dorsispinatus, Labidocera rotunda, Calanus sinicus, Euchaeta concinna, Zonosagitta bedoti, and Labidocera euchaeta. In autumn, 45 species in 12 groups were identified, with 5 dominant species: Centropages dorsispinatus, Zonosagitta bedoti, Diphyes chamissionis, Beroë cucumis, and Calanus sinicus. The abundance and biomass of zooplankton were greater in summer (143.97 ind/m³ and 176.34 mg/m³,respectively) than in autumn (21.38 ind/m³ and 86.28 mg/m³,respectively). The Shannon-Wiener diversity index was higher in summer (3.03) than in autumn (2.82), and Pielou's evenness index was lower in summer (0.64) than in autumn (0.83). Furthermore, according to our MDS analysis, zooplankton community composition was highly variable in summer, but not in autumn. The results of the CCA showed that temperature, salinity, chlorophyll a, and nutrients were the main environmental factors that affected the zooplankton community. Finally, we compared our results with historical data and found that zooplankton abundance and biomass has declined in the Zhoushan Sea, but the dominant species have remained relatively stable.