Abstract: The community structure and environmental parameters data collected from Yellow River estuary and its adjacent area in July, 2009 and September, 2010. The result showed a significant difference in zooplankton community characteristics between summer and early autumn. The species richness and abundance in summer (65 taxa, including 14 species of larval, 295.5 ind/m³) were greater than in early autumn (54 taxa, including 15 species of larval, 229.6 ind/m³). Besides, the biological diversity in summer was higher than in early autumn. There was a significant difference in dominant species between two seasons. Calanus sinicus, Paracalanus parvus, Labidocera euchaeta, Sagitta crassa, Macrura larva, et al. Showed dominance in summer, while Eirene ceylonensis, Pleurobrachia globosa, Centropages dorsispinatus, Sagitta crassa, et al. showed dominance in early autumn. Warm-water species (C. dorsispinatus) and small medusae (E. ceylonensis and P. globosa) became dominant species in this area that had never been reported before, this is worthy for attention and ongoing observational studies.