Based on the minute precipitation data from 1973 to 2014 at Huludao, we establish rainstorm statistical samples. The revision of rainstorm intensity formula at Huludao was carried out by the annual maximum value method. The probability curves were followed by P-Ⅲ distribution, and the formula parameters were calculated. The rain intensity calculated by the old formula from 5 to 30 minutes of each return period are lager than that calculated by the new method. The rain intensity calculated by the new and old formula of 45 minutes of each return period are basically equivalent. The rain intensity calculated by the new formula from 60 to 180 minutes of each return period are lager than that by the old method. Based on these results, the designed rainstorm pattern at Huludao is studied. Using the coefficient of rain peak position of 0.32, and the designed rainstorm pattern of the Chicago, the accumulated precipitation of rainstorm pattern of return period of 2 a lasted 60, 90, 120, 150, 180 minutes are between 38.73 to 66.99 mm. It increases slowly early in the precipitation, but increases faster around the rain peak, then increases slowly again.