Abstract: In this paper,based on the data of raindrop from 1960 to 2014 in Lanzhou National principal station,the Direct-fitting method,Gumbel distribution function and Pearson-Ⅲ distribution function were used to study the rainstorm intensity formula. The Chicago rain pattern were used to study the rain peak coefficient,then combining with the rainstorm intensity formula,the short duration rainfall pattern is determined. The main result as following: (1) Pearson-Ⅲ distribution function is better than both Direct-fitting method and Gumbel distribution function,meanwhile the rainstorm intensity parameter A1 of 1a is 5. 532 mm/min after adjustment,the return period adjustment parameter c is 3. 198,the rainfall duration offset parameter b is 14. 92 min and the mean absolute mean square error is 0. 036 mm/min. (2) The Pearson-Ⅲ distribution function can satisfy different rainfall durations and longer reproduction period. The simulation accuracy of rainstorm of the rainfall duration less than 90 min and the return period more over 20 a is better than other situations,meanwhile the mean absolute mean square error is minutest 0. 03 mm/min of the return period ranged from 2a to 20 a.