According Based on the sample collected from the environmental survey in the Hang Zhou Bay, the East China Sea during the period of August 2011, the distribution of biomass and abundance of zooplankton were analyzed, and relations between the community structure and environment were described in this paper. The results showed that there existed 44 species of zooplankton, of which, the plank tonic copepods and other larval were accounted for 50%, the jellyfish and fish were 15.9% and 9.1% respectively. The dominant species were Labidocera euchaeta, Tortanus vermiculus, Pleurobrachia globosa and Acanthomysis longirostris etc. The biomass and abundance of zooplankton ranged from 8 to 4050 mg/m3 and 7 to 723 ind./m3, and the average biomass and abundance were 370 mg/m3 and 77 ind./m3. Diversity index of zooplankton of Hang Zhou bay was the middle level, which ranged from 0.52 to 2.56 and average value was 1.70. The zooplankton in the surveyed area could be divided into 3 ecotypes, which were coastal low saline species, estuary brackish water species and offshore warm water species.