In order to study hypoxia in the main estuaries and adjacent coastal areas in China, we compared the hypoxia in the estuaries of the Yangtze River, the Pearl River, and other rivers, and analyzed the factors. We found that hypoxia mainly occurred in the estuaries of the Yangtze River, the Pearl River, and the adjacent coastal areas; it had the most significant increase in the summer(from June to August)and disappeared in the autumn and winter. The hypoxia zone in the Yangtze River Estuary was mainly located in the area with latitudes from 30. 75°N to 32°N and longitudes from 122. 5°E to 123. 25°E, and there were two hypoxia centers in the south and north, respectively. The degree of hypoxia in the Pearl River Estuary was relatively moderate, and hypoxia mainly occurred from the Huangpu section to Humen waters in Guangzhou and in the Lingdingyang Channel. In addition, hypoxia occasionally occurred in the estuaries of the Liaohe River, Qiantang River, and Haihe River. We also found that hypoxia was subjected to many environmental factors, of which the stratification of water was one of the initial factors and the decomposition of terrigenous pollutants was a major factor of oxygen consumption. Tides, upwellings, nutrients, and chlorophyll-a had different influences on the scale, degree, and duration of hypoxia, due to the various characteristics of the estuaries.