Using the minutely precipitation data during 1981-2013, which is from the stations of Shapingba, Beibei, Banan and Yubei in the main urban areas of Chongqing, the rainstorm intensity formula fitted by the Pearson Ⅲ distribution, Gumbell distribution and exponential distribution was made respectively by using the annual multisampling method and annual maximum value method. The results show that rainstorm intensity calculated by the formula using annual maximum value method is less than that calculated by the formula by annual multisampling method for the reappearing period less than 10 years. In the 10-30 years reappearing period, the difference of the two is slight, and the rainstorm intensity calculated by the formula according to annual maximum value method is more than that calculated by the formula according to annual multisampling method. The error of rainstorm intensity formula according to annual multisampling method is the least for the four stations. The rainstorm intensity formula of Beibei and Banan is made fitted by exponential distribution according to annual multisampling method based on the precipitation data from 1981 to 2013. The rainstorm intensity formula of Yubei and Shapingba is made fitted by exponential distribution according to annual multisampling method based on the precipitation data from 1991 to 2013. The applicability of new formula to calculate the rainstorm intensity in the main urban area of Chongqing is determined by analyzing the spatial distribution features of precipitation in different times.