Abstract: At present, design precipitation especially Chicago rainstorm pattern, has been widely used as the input in current urban flooding researches. Due to the generalization of this method, in the actual flood control applications and urban hydrological processes research, it is necessary to further explore the related problems and defects when using Chicago rainstorm pattern to characterize disastrous precipitation. Based on the flood-causing precipitation events that occurred in Zhengzhou City from 2011 to 2018, this paper summarized the annual evolution trend of flood-causing precipitation, and then compared the process information of Chicago rainstorm pattern design precipitation and actual flooding-causing precipitation in terms of peak distribution, intensity and so on. Based on the storm water management model (SWMM), emergence and development distinctions of actual urban flooding with different formation causes in the study area were analyzed, and they were compared with that of floods input by Chicago rainstorm pattern. Results indicated that: ① During a year, the transition of flood-causing precipitation in Zhengzhou City urban area was from intensity-caused precipitation to dual-caused precipitation, and then to volume-caused precipitation. ② The flooding process of 2-year Chicago rainstorm pattern in study area was similar to the volume-caused precipitation, while floods caused by 5-year and higher standard Chicago rainstorm pattern had the characteristics of dual-caused precipitation. ③ The flooding process of intensity-caused precipitation had short duration and incomprehensive impact, and that of volume-caused precipitation had long duration, while dual-caused precipitation had both above disaster-inducing mechanisms with more wide influnces. The research results have certain significance and important value for urban waterlogging control, sponge city construction and regional flood mitigation.