Under the background of global climate change and rapid urbanization, extreme climate events occur frequently and flood disasters occur in highly urbanized areas. Considering that frequent human activities have an important impact on regional water cycle and the high concentration of population and wealth makes the vulnerability of disaster bearing bodies increasingly prominent. Taking the Pearl River Delta with rapid urbanization and high concentration of economic factors as the research area, this paper combed the development process and characteristics of regional urbanization, and analyzed the temporal and spatial evolution characteristics of rainfall structure and its relationship with urbanization development. The results show that from the perspective of rainfall duration, the rainfall events are mainly short duration rainfall within 6 h, but the main contribution of precipitation is long duration rainfall more than 6 h, and the rainfall structure has not changed significantly. From the perspective of rainfall grade, rainfall events are mainly weak rainfall, but the main contribution of precipitation depends on the less frequent heavy rainfall events. The rainfall structure has changed significantly, the incidence of medium and heavy rain has increased significantly, and the incidence of light rain has decreased significantly. The change of rainfall structure in highly urbanized areas is the most obvious, the incidence of medium, heavy rain and storm increases significantly, and the incidence of light rain decreases significantly.