Abstract: Based on the ground observation precipitation data from May to September in 2018~2019 and August in 2020 in Sichuan province, including the automatic station data, combined with the forecast field data of each element of the model starting from 8:00 in southwest region of the same period, the localization of the minimum deviation and correction method for predicting the start time of short-time heavy precipitation was carried out, and the method was used to correct the start time of heavy precipitation events in August 2020. The results show that the correction method of the minimum deviation sum could determine the correction threshold and the optimal threshold percentage of the physical factors related to the start time of heavy precipitation. From the correction effect of heavy pricipitation in August 2020, the method had a certain ability to correct the start time of short-time heavy precipitation, and the deviation of the start time of heavy precipitation was reduced by 2~8 hours.