Abstract: This paper proposes an assessment model of the regional rainstorm process based on the return period method, which is used to comprehensively assess the frequency and intensity of rainstorm processes. Based on the hourly rainfall data and rainstorm disaster data of 114 regional rainstorm processes in Chongqing from 2011 to 2021, the probabilistic fitting, return period calculation, correlation analysis and other methods are used to construct the return period assessment model of regional rainstorm processes, and the business verification is carried out. The results are as follows: (1) Using the return period calculation formula built in this study, the error between the return value and the original value of the rainstorm process characteristic quantity is less than 10%, suggesting a higher accuracy of the return period calculation. (2) The correlation coefficient between the constructed return period assessment model and direct economic loss is significant at the significance level of 0.001, which shows a 16% improvement compared to the current business index. (3) Historical backtracking and independent sample tests show that the grade consistency rate between the return period evaluation model and business index is 70%. The return period assessment model is stable and can reflect the frequency and intensity of events, which can provide a new idea for regional rainstorm process assessment.