A total of 58 years self-recording rainfall records at Guilin National Weather Station from January 1957 to December 1957 were used. Using the annual maximum sampling method,11 short-duration maximum rainfall records in every year were selected,and statistical samples of rainstorm intensity formula were obtained. Fitting of statistical samples was conducted by using three kinds of frequency distribution curves: Pearson-Ⅲdistribution,Gumbel distribution and exponential distribution. The formula of rainstorm intensity was derived by the least square method and Gauss Newton method,and then the accuracy of results was inspected. The results showed that the fitting effect based on the Pearson-Ⅲdistribution and Gumbel distribution was better than that of the exponential distribution;the accuracy of rainstorm intensity formula based on Pearson-Ⅲdistribution was better than that of Gumbel distribution and exponential distribution;the accuracy of rainstorm intensity formula derived by the least square method was better than that of Gauss Newton method;the accuracy of interval parameter formula of rainstorm intensity was better than that of rainstorm intensity formula.