The accuracy of urban storm intensity formula directly affects the planning and design of urban pipe network. The existing formula which can not reflect the characteristic of local rainfall should be revised. In this paper, we took the rainfall data of Zhengzhou as an example to derivate urban storm intensity formula by two different storm sample selection methods (the annual maximum value method and annual multi-sampling method). Comparing these two methods, we found the annual maximum value method is not only easy operation, but also can be used to make contrastive analysis with hydraulic engineering in the same condition. This method benefits popularizing and revising urban storm intensity formula.