Rainfall and tides are two important factors of urban waterlogging. A risk analysis of rainfall and tidal levels is important to reduce waterlogging disasters and protect people’s lives and property. It has been difficult to define and calculate return periods and design values. In this study, by constructing the joint distribution of 1-hour maximum annual rainfall and the corresponding tidal levels, we defined the secondary return period and proposed calculation methods, to point out the differences in the identification of dangerous regions between the secondary return period and traditional return periods. The results of data analysis show that the definition of the secondary return period is more precise. The design value based on the secondary return period is reasonable. It can provide useful information about the risk analysis of waterlogging.