Abstract: Based on the reanalysis data of NCEP and high-resolution numerical simulation data of WRF-ARW, the characteristics of atmospheric heat and precipitation during the heavy rain in Sichuan Basin from August 10 to 12, 2020 were diagnosed and analyzed by using the atmospheric apparent heat source and apparent moisture sink equation. The results show that at the beginning of the rainstorm, a large amount of water vapor collected in the middle and bottom layer of the convection, which was rich in water vapor for the coming of the rainstorm. At the time of rainstorm, the apparent heat source and apparent moisture sink increased significantly in the middle and upper layers of convection, resulting in deep heating and humidification layer in the middle and upper layers of troposphere, which indicated that the cumulus convective cloud was active and the convective precipitation was the main precipitation. At the same time, it was found that the vertical term played a major role in the occurrence and development of rainstorm by decomposing atmospheric apparent heat source and apparent moisture sink, which fully demonstrated that the strong upward movement could bring abundant water vapor, which was beneficial to the development of rainstorm.