Abstract: Based on the precipitation data carried out by the annual maximum value method for 1959 to 2014 in Xinxiang city, we analyze the variety characteristics of heavy rain, and find that the characteristics have changed significantly since 1979, so that the old rainstorm intensity formula had lost applicability. The optimal rainstorm intensity formula was chosen by using curve fitting, computing and significance testing with the Pearon Ⅲ distribution, gumbel distribution and exponential distribution. Comparison of the old to the new formula shows that the new formula has a better applicability.