In order to meet the engineering design requirements for longer duration and higher return period extreme rainstorm under changing environment,based on the data of long series short duration rainstorm in different rainstorm areas, analyzed the variation characteristics of design rainstorm time history distribution.The formula form of four parameter, two variable exponential function long duration comprehensive rainstorm is given, the parameter calculation method is defined, and the accuracy is evaluated.The results indicate:(1)The intensity of rainstorm in Yunnan is about twice different among regions. With the increase of time, there is a variation point of rainstorm intensity in each region at 1h, and another variation point in the east and northeast is at 12 h.(2)The formula form of long duration comprehensive rainstorm based on exponential function can simplify the calculation process, meeting the calculation requirements of design rainstorm with duration of 10 min-72 h and return period of 2-100 a, and the simulation accuracy is better than the current rainstorm formula as a whole.The simulation accuracy can be further improved by considering the variation characteristics of rainstorm.(3)The formula of long duration sectional comprehensive rainstorm in eight typical rainstorm areas in Yunnan Province is established. The absolute root mean square error is 0.012-0.028 mm/min, the relative root mean square error is 2.7 %-4.4 %, and the qualification rate is 100 %.