This research aims to study the source， spatial distribution characteristics and ecological risks of diuron in the coastal waters of the Yangtze River Estuary and Shanghai， water samples from 24 stations in the coastal waters of the Yangtze River Estuary， Hengsha Island （inland） waters and the waters near the Yangtze River Estuary Chinese sturgeon reserve were collected from October to November 2021， and the content of diuron in the surface water samples of each station was analyzed by solid phase extraction and high performance liquid chromatography tandem mass spectrometry. According to the test results， the mass concentration of diuron was detected in the water samples of 24 stations in three different regions. Among them， the detection range of diuron mass concentration at 10 stations along the Yangtze River Estuary in Shanghai was 182.43-439.38 ng/L， and the detection rate was 100%. The detection range of diuron mass concentration at 9 stations in Hengsha Island （inland） water area is 83.48-369.25 ng/L， and the detection rate is 100%. The detection range of diuron mass concentration at 5 stations near the Chinese sturgeon reserve is 1.97-2.85 ng/L， and the detection rate is 100%. The spatial distribution of diuron is mainly affected by factors like water transport， ship maintenance， agricultural activities， tides and seawater dynamics. Besides， the ecological risk assessment shows that the coastal waters along the Yangtze River Estuary in Shanghai are potentially at medium risk. Farming areas in Hengsha inland waters are at medium risk， and the nearby waters of the Nature Reserve are at low risk. The results show that the environment in the coastal waters of the Yangtze River Estuary in Shanghai is being threatened by the diuron， especially in the major ports and docks along the Yangtze River Estuary in Shanghai as well as the agricultural areas and river intersections in the Hengsha Island area. Although it will not threaten the Chinese sturgeon reserve in the short run， it still deserves attention.