Global warming is an indisputable fact, and the increase and intensification of extreme climate events caused by it have become a global trend. In recent years, there is a trend of drought and flood coexisting and frequent drought and flood in many regions of the world. Studies suggest that the main reasons for the frequent occurrence of long-term drought and flood are the strong non-uniformity of water cycle on time scales caused by global temperature rise and the increase of aerosol particle emitted by human activities. The main reason for the rapid conversion of drought and flood in short term is the coupling effect of the atmospheric circulation and the anomalous transport of warm and wet air mass. At this stage, there are fewer observations, diagnoses, and simulations about the simultaneous frequency of extreme precipitation and drought events. The relationship between them under different climatic and geographical conditions and the key factors causing the variation of regional precipitation intensities are in urgent need of further study.