For urban design storm, there are some features which are shorter duration and lower design level. It differs from commonly used method of frequency computation. In this paper, the calculated formula related to empirical frequency are corrected, inverse S-shape distribution to fit the storm series by empirical curve-fitting technique is suggested, and the results which is on safe side by using the excess a specific-value method are recognized.ln addition, the storm intensity formula of some city in China are listed. There is no certain rule to its parameters. It is hoped that further study is needed to harmonize the parameters from single to areal sites.