Based on the daily precipitation of 24 global climate models from the sixth phase of the Coupled Model Intercomparison Project 6 (CMIP6) multimodel simulations, the generalized extreme value distribution (GEV) is introduced to study the risks of precipitation extremes that expected to occur every 20, 50 and 100 years over China under 1.5/2°C global warming. Compared to the historical period (1995-2014), the changes in the probability risks of extreme precipitation under global warming of 1.5/2℃ present an overall increasing trend. Although their spatial distributions show similar characteristics, the additional half a degree global warming will lead to a higher risk. For example, extreme precipitation that occurred once every 50 years will become once about every 17/14years under the warming of 1.5/2°C, respectively, and extreme precipitation will become more frequent. There are regional differences in the responses of different regions to climate warming, among which the middle and upper reaches of the Yangtze and Yellow Rivers and the Qinghai-Tibet Plateau region in the Western China, and the middle and lower reaches of Yangtze and Yellow Rivers and its south in Eastern China, are highly sensitive response regions to climate change, and their probability ratios reach 3 or even 5 or more. Furthermore, the influence and contribution measures of location and scale parameters on the probability ratios are explored from a theoretical perspective based on the probability distributions, and are used to explore the influences of the climate means and variability changes on the risks of extreme precipitation. The results show that there are significant differences between Eastern China and Western China in the incremental changes of location and scale parameters, and in the rates of probability risk changes, which lead to differences of the factors that influencing the risk of extreme precipitation. In the Western China, although the changes in climate means and variabilities of extreme precipitation are small, the probability ratios increase significantly due to the high rates of probability risk changes. In contrast, the change rates are small, but the climate means and variabilities present a high increase, which also lead to an increase in the Eastern China. Moreover, compared to the location parameters, the increase risks in most of regions over China are mainly due to the changes of scale parameters of extreme precipitation in the future.