Based on observations from automatic weather stations, the extremes, periods and hourly variation characteristics of precipitation and the urban flooding influence are analyzed for the “7·20” extreme rainstorm in Zhengzhou City, Henan Province, and some suggestions on the prevention and control of waterlogging under over standard precipitation conditions are put forward. The results show that this is an extreme precipitation weather process, and can be divided into five obvious precipitation periods. The short-term heavy precipitation shows characteristics of frequent occurrence and repeated occurrence at the third and fourth periods, while the continuous precipitation heavier than 80 mm/h in the main urban of Zhengzhou from 12:00 to 18:00 CST on 20 July is the principal cause of the serious urban flooding. The current design standards of unban flooding prevention is not enough to prevent precipitation with this intensity in the main urban area of Zhengzhou City, but we could reduce the flooding disasters by improving the emergency system of urban flooding prevention while exceeding standard, raising the urban flooding prevention standards at prone points, and measures like this.