Abstract: Aiming at the development and evolution of the southwest vortex during two heavy rainstorms in western Sichuan Basin, the hourly reanalysis data of ERA5 data from the European Centre and the TBB data of FY4A were used for diagnostic analysis. The following conclusions are obtained: The southwest vortex of the two processes was generated under the favorable circulation background of the eastward movement of the Trough and westward extension of the subtropical high. In the first process, the southwest vortex was generated and developed in a high-energy and high-humidity environment, and the sensible and latent heat heating effects in the lower layers were more significant. The positive vorticity developed westwards with height and reached 400 hPa. The vorticity extension and torsion terms played a major role in the development of the southwest vortex. In process 2, the southerly airflow was stronger, and the divergent pumping effect in the upper troposphere was stronger. The thermal condition was weaker than that in process 1, and the southwest vortex was in a high humidity state, The strong sensible heat and latent heat of condensation heating in the upper troposphere warmed the upper layer, thereby enhancing the development of the southwest vortex. The positive vorticity of the southwest vortex developed to the tropopause, and the positive vorticity column developed vertically with height, The dynamic effect was stronger than that of process 1, and the vorticity stretching term, torsion term and vertical transport term played a major role in the development of the southwest vortex.