Abstract: Using high-altitude and ground-based observation data, hourly reanalysis data of ECMWF(ERA5) and fy-2h satellite TBB data, 7.15 heavy rain and 8.24 heavy rain that happened in the southern Sichuan Basin were analyzed. The results showed that The results show that : (1) The two rainstorm processes occur in different circulation situations. The environmental conditions of high energy and high humidity in the basin and the favorable system configuration in the middle and lower layers are the main causes of the two rainstorm processes, and the diffusion of cold air near the surface layer southward is another key factor triggering the 8.24 rainstorm. (2) During the 8.24 rainstorm, the water vapor and energy in the lower layer are more sufficient, the atmospheric stratification is more unstable, and the rainfall range and intensity are larger. (3) In the 7.15 rainstorm process, the mesoscale convective cloud cluster is eastward, and the cold air path in the 8.24 rainstorm process has a certain influence on the birth of the mesoscale convective system, which makes the convective cloud cluster more westward.The heavy rainfall occurs in the mature stage of the mesoscale convective system, and the strongest rainfall period corresponds to the strongest period of the cold cloud center.