The hourtohour precipitation data in the recent 10 to 40 years in Xi’an and waterlogging information from the local government are used to analyze the formation causes of waterlogging induced by severe rainfall. The shorttime severe rain, or rain with large amount, is the direct cause for Xi’an’s waterlogging, and the drainage capacity is also a key factor. Along with the development of Xi’an’s urbanization, both the intensity of severe rainfall and the number of severe rains with 1hour precipitation being greater than 10 mm increase. The increased frequency of severe rains increased the frequency and intensity of waterlogging, and the urbanization is the main cause of the enhanced urban waterlogging. The simulation analysis using the Waterlogging Numerical Model reveals that the thresholds of rain intensity for waterlogging in Xi’an are relatively low, 3 mm/h for waterlogging and 13 mm/h for severe waterlogging. The northwestern part of Xi’an is the most critical zone for weather forecasting, disaster monitoring and municipal waterlogging defense departments. Generally speaking, to shorten the distances between drainage wells is an effective approach.