Abstract: Using the minutely precipitation data from 1974 to 2014 of Jingmen weather station, rainstorm intensity formula are derived based on the annual maximum value method, in which exponential distribution, Gumbell distribution and P-Ⅲ distribution are chosen, respectively, to get the rainstorm intensity-listing time-return period form.The rainstorm intensity formulas are calculated by the least square and Gauss-Newton methods, and the best one is chosen.The results show that the relative root mean square error by the P-Ⅲ distribution is much smaller.The integral formula is made by the P-Ⅲ distribution and the least squares method.The total formula is made by P-Ⅲ distribution and Gauss-Newton method.The rainfall intensity calculated by the latest integral and total formulas are overall larger than the currently being used one, suggesting that it's necessary for the relevant departments to increase the pipe size when designing the underground pipe networks.At present, the formula have been published and executed by the government of Jingmen city.