Abstract: Extreme events such as floods have brought serious ecological impacts and huge economic losses to our society,but the mechanism of these extreme events has not been fully understood. This paper takes the Yangtze River basin as the research area,and selects discharge data from 224 hydrological stations,and meteorological data measured at 247 meteorological stations in the Yangtze River Basin. Extreme precipitation and soil water storage are taken as flood driving forces. Our results show that both extreme rainfall events and floods occur from May to August,and the occurrence time of extreme events in different watersheds is related to latitude. For the dominant mechanism of floods,there are different dominant drivers in different regions,and there is a certain correlation between the dominant factors and the basin area.