Abstract: Overflow of combined sewer network after rain is one of the important causes of black and odorous urban water after rain, and rainfall is the key influencing factor. In this paper, the precipitation in the Yangtze River Basin and the risk of urban black odor after rain were systematically analyzed. The influence mechanism of rainfall on the risk of urban black odor was reviewed. The risk assessment method of black odor based on rainfall frequency was proposed and predicted. The study found that moderate rainfall and above intensity rainfall are more likely to cause combined sewer overflow and increase the risk of black and odorous water. Through the analysis of the rainfall characteristics of 88 cities in the Yangtze River Basin, it is found that the rainfall frequency in the upper reaches is higher, but the rainstorm grade is less. The proportion of heavy rain and rainstorm in the rainfall composition of the middle and lower reaches is higher. Based on the rainfall data from 2019 to 2023, the Z distribution method is used to classify the frequency of moderate and above rainfall in cities. The results show that the frequency of rainfall in the middle and lower reaches of the Yangtze River is higher, especially in Anhui, Hunan and Hubei provinces. The results of the study combined with the distribution of historical black and odorous water bodies in the Yangtze River Basin in China, and analyzed the possibility of the influence of rainfall pattern frequency on the black and odor return of urban water bodies, in order to provide a basis for the management of black and odor return of urban water bodies.