Abstract: The differences of rainfall between urban and rural regions in Nanjing from 2009 to 2013 were analyzed based on the hourly rainfall observation data from 71 intensive automatic stations.The results indicate that there is an obvious seasonal difference for the rain-island effect in the urban region.The urban rain-island effect mainly occurs in June to August,especially in July and August.There is no significant difference in rainfall amounts between urban and rural regions in the other seasons.The rainfall amounts for light,moderate and heavy rains also have no apparent differences between both of the regions,However,there are evident differences in rainstorm and short-time heavy rainfall during June to August in Nanjing due to the urbanization.The rainstorm frequency and intensity and the frequency of the short-time heavy rainfall in the urban region are higher than those in the rural region.So,it is easy to form an urban flood disaster.The urbanization has little impact on the differences in general rainfall between urban and rural regions,while it significantly makes the disaster rainfall events,such as summer rainstorm and the short-time heavy rainfall intensification.