Flood control schemes and the scale of drainage facilities are closely related to the occurrence of rainstorms and the tide level of an outer river, so it is necessary to study the probability of the occurrence of rainstorms and the tide levels. Based on the daily rainfall and tide level data of Jiangyin station from 1956 to 2018 in the Wuchengxiyu region of Taihu Lake basin, copula functions were used to establish the joint distribution function of annual 1-day, 3-day, 7-day, and 15-day maximum rainfall and the highest tide level of the Yangtze River for different return periods . Based on this information, a risk probability model was constructed to evaluate the flood and tidal risks. It was found that when the design criteria of rainfall and tide level were similar, the probability of the simultaneous occurrence of rainfall and tide level greater than their respective magnitudes was significantly less than their respective design frequencies. The encounter combination analysis method proposed in this study has a wide application prospect for flood control and drainage design.