The computer model of drainage sewer and conduit system often needs to use the design storm as the rainfall input, and the design storm based on the storm intensity equation is one of the common methods. The structural methods of uniform intensity storm, triangular storm, alternating blocks storm and Chicago storm are analyzed; The characteristics of peak storm intensity, rainfall depth and rainfall peak position coefficient of these storm patterns, as well as the runoff characteristics such as peak flow, total runoff and time to peak flow formed in the catchment area are illustrated by examples. Among them, the peak intensity, rainfall depth and peak runoff caused by Chicago storm are large, and the time to reach the peak runoff is short. In the risk-based rainwater pipe and canal system design, the calculation results are relatively conservative, so Chicago storm is recommended to use.