Abstract: With the profound impact of climate change and strong human activities on the urban water cycle, the frequency and intensity of floods and waterlogging disasters in most cities in China are increasing, as well as the risk of floods and waterlogging disasters. In order to conduct in-depth research on urban flood problems and their causes, we took the typical mountainous plain prototype city of Jinan City with prominent flood disasters such as flood disasters and rain and flood disasters as an example. By using the Mann-Kendall, Morlet wavelet, and Sen′s slope estimation methods, we analyzed the characteristics of rainfall and runoff changes in the urban area of Jinan City from 1950 to 2020, explored the mechanism of urban hydrological cycle, analyzed the formation mechanism of urban floods, and deeply analyzed the causes of urban flood problems from climate, topography, and human activities three aspects. The research results showed that the annual rainfall and runoff in the main urban area of Jinan City were increasing, and the main disaster causing factors of urban flood disaster were frequent short-term heavy rainfall events and the influence of lower terrain in the main urban area. It is predicted that the frequency and intensity of extreme rainstorm in Jinan will increase in the future, and the urban flood disaster may be more serious. The research results can provide a reference for urban flood disaster warning and forecasting.