In order to reinforce the scientific part of the prevention and mitigation of rainstorm disasters, based on the hourly precipitation data of 126 national weather stations from 2010 to 2019 and basic geographic information, we build the model of risk assessment of rainstorm disasters through three aspects: the danger factor of disaster-inducing, the sensitivity of disaster-pregnant environment and the vulnerability of the disaster-bearing body. To realize the division of risk areas relating to rainstorm disasters in Yunnan, we apply four methods: maximum entropy, natural break point, ArcGis interpolation and grid analysis. Results show that the high-risk areas of rainstorm disasters centre in the southern Yunnan, including Xishuangbanna, Pu’er, the southern Honghe and Dehong. However, Diqing, Nujiang and the northern Lijiang are lower-risk areas. Throughout the whole rainstorm disaster in Yunnan, high-risk and secondary high-risk areas account for 7.05% and 25.22%, and low-risk and secondary low-risk areas account for 10.32% and 21.86%. Using the data, such as the times of rainstorm disasters in 2020 and the testing results of area-division of rainstorm disasters, it is shown that the area-division assessment is scientific and rational.