Abstract:Based on the hourly precipitation data from national meteorological stations of China and the definition method of extreme precipitation with percentile threshold, this paper makes a statistical study of the spatio-temperal distribution and diurnal variation of hourly precipitation in China from April to October in 1951-2021. The results show that the hourly precipitation thresholds of the main rainy season in China are large in the southeast but small in the northwest, and there are four large threshold value centers lo-cated in South China, the Circum-Bohai Region, the middle and lower reaches of the Yangtze River and the Sichuan Basin. With the increasing extremeness, the hourly precipitation threshold in northern China increases more significantly than that in southern China, and the large threshold center moves northward. On the monthly time scale, from the south to north of China, the month with the highest frequency of hourly precipitation is postponed from May to August and the latest month is in West China (September-October). As the extremeness increases, the month with the highest frequency of precipitation is postponed from June-July to July-August, and the regional differences are reduced. In terms of diurnal variation characteristics, the frequency proportion of hourly precipitation of China presents a main valley-peak cycle from afternoon to night and a sub-cycle from midnight to morning. With the increasing extremeness, the amplitude of the main cycle increases and the peak value of the sub-cycle decreases. From the perspective of different geographical locations, the peak time of extreme hourly precipitation in Sichuan Basin is in the early morning, while the peak time in other three areas is consistent with the mean of whole China. The diurnal variation amplitude declines gradually from south to north of China, with the largest amplitude in weastern China. The peak time of hourly precipitation has the characteristics of spatial concentration. The night peak is mainly concentrated in North China, Northeast China and southern coastal areas of China, while the morning-to-forenoon peak is concentrated in the central, east, southwest and the parts of northwest of China. And the gradual delay and abrupt change in spatial distribution of precipitation peak time are closely related to land-sea distribution and large topography. The diurnal variation characteristics of the spatial proportion and frequency proportion of hourly precipitation peak time are similar, both featured with gentle peak in the morning and steep peak at night. This is because the time of the night peak is close to the time at different stations, but the time of the morning peak is not so. Furthermore, with the increasing extremeness, the main peak of frequency proportion at night increases significantly, but the main peak of spatial proportion at night is almost unchanged. This difference is because the change of frequency is mainly caused by the change of frequency at the same stations, rather than the difference between different stations.