Based on the rainstorm data from the middle and lower reaches of the Chuhe River in the period from 1959 to 2010 and the tide level data at Xiaguan Station in Nanjing City, a joint distribution function of the annual maximum 1-day, 3-day, and 7-day rainstorms and the corresponding tide levels of the Yangtze River with different return periods was built based on the Copula function. The encounter probabilities of the design rainstorm and different tide level intervals and the encounter probabilities of the design tide level and different rainstorm intervals were calculated. The results are similar to conclusions in the Nanjing Urban Flood Control Planning, indicating that the calculation method is reasonable and feasible and can provide a reference for combined calculation of rainstorm and tide level.