Abstract: The process of a heavy rainfall in Wenchuan on July 13, 2023 was analyzed by using upper-air weather charts, automatic station observation data, NCEP reanalysis data and satellite cloud images. The results show that the weather process was located in the atmospheric environment outside the subtropical high, which was caused by the combined action of the low trough in the western Sichuan Plateau and the southwest warm and humid air flow outside the subtropical high. The high relative humidity and southerly air transporting water vapor provided sufficient water vapor conditions for heavy rainfall. Strong upward movement and vertical uplift provided sufficient dynamic conditions for heavy rainfall. The high unstable energy provided good thermal conditions for the precipitation.