@@ According to the function and the role of zooplankton in the marine food web, the zooplankton in the Yellow Sea ecosystem could be separated into 6 functional groups: Medusae, Chaetognaths, Salps, Euphausia, Calanus and Paracalanus. From the point of biomass, which was the basis of the food web, and feeding activities, the contribution of zooplankton functional groups to the ecosystem were estimated; the distribution pattern, seasonal change and the species composition of each functional group were analyzed. The Euphausia group composed of the species that the body length was more than 5 mm, e.g. Euphausia pacifica; the Calanus group was comprised mainly of large copepods, 2-5 mm of body length, e.g. Calanus sinicus, while the Paracalanus group was dominated by small copepods (< 2 mm), e.g. Paracalanus parvus. These three groups were the main contributors to the food for.