Abstract: In this paper, we described the spatial distribution of the hypoxic zone in the world and discussed its formation mechanisms, sea surface features, and seabed geochemical and biological characteristics. The benthic foraminiferal assemblages found in the Yangtze River Delta were compared with those in the hypoxic areas of the world. It is found that the species of Epistominella naraensis, Bulimina marginata, Bolivina spp., Florilus spp., Ammonia spp. and Bulimina spp. are sensitive species in the hypoxic zone of the Yangtze River estuary and can be used as a proxy to denote a low oxygen environment for study of the hypoxic events in the history. However, selection of right foraminiferal assemblages is required before environmental interpretation is made.