Abstract: To analyze the relationship between the urbanization development degree and extreme rainfall change, hourly rainfall data from 22 rainfall stations in the Pearl River Delta region from 1973 to 2012 were selected. Methods such as spatial analysis, linear regression, sliding average, and the Mann-Kendall trend test were used to analyze the spatiotemporal distribution and variation characteristics of extreme rainfall and rainstorm patterns in the Pearl River Delta region under the sense of high urbanization. The results showed that extreme rainfall in highly urbanized areas of the Pearl River Delta increased by 44.3 mm/(10 a), showing a significant increase in the trend, while the other adjacent areas showed no significant change. The significant increase in extreme rainfall during the first rainy season was the main reason for the increase in the annual extreme rainfall in highly urbanized areas. In addition, the rainstorm pattern in the Pearl River Delta region was dominated by unimodal patterns, among which the proportion of type Ⅰ rainstorms was the highest (approximately 33.7%). The occurrence frequency of type Ⅰ rainstorms in highly urbanized areas has increased significantly, which easily leads to an increase in rainstorm flooding events. Therefore, flood control and drainage work in highly urbanized areas should be strengthened.