Eutrophication seriously endangers the water environment security of river basins and regional ecological health. The Yangtze River Basin is one of the most important ecological regions in China. With the intensification of pollution due to economic development, it is confronted with the problem of eutrophication. This paper assesses the eutrophication risks of the Yangtze River Basin and conducts a spatio-temporal characteristic analysis using the logarithmic power function index method. The results show that the concentrations of various water quality indicators exhibit a seasonal variation trend. The Yangtze River Basin is generally in a eutrophic state, mainly affected by total phosphorus and organic pollution. In terms of time, eutrophication is more severe during the transition period between spring and summer. Spatially, the occurrence of eutrophication is concentrated in the middle and lower reaches of the Yangtze River Plain and coastal areas. The above research results provide references for pollution control, water quality improvement and ecological protection in the Yangtze River Basin.