China has at least 30 oyster species, all of which provide valuable ecosystem services. Oysters’ filter feeding habit reduces suspended particles and nutrients. One hectare of oyster reef can clean a volume of water equivalent to nearly 15 Olympic swimming pools daily. Oysters’ excrement can stimulate denitrification by removing nitrogenous organic matter, helping to mitigate eutrophication. Natural oyster reefs provide habitat for many species, enhancing biodiversity and increasing fisheries. Oyster reefs can reduce impacts of waves caused by hurricanes and typhoons, stabilizing shorelines. Despite their ecological importance, 85% of oyster reefs globally have been degraded since the 19th century by overharvesting, coastal development, water pollution, and disease. China’s oyster reefs, especially those in Tianjin and Jiangsu, have been seriously damaged during recent decades. Urgent action by Chinese authorities is required to protect these crucial species.