Abstract: Based on conventional observation data and satellite data, a rainstorm process in Yibin City on September 3, 2021 was preliminarily analyzed from the aspects of large-scale circulation situation, thermal and unstable conditions. The analysis shows that this heavy rain was a weather process caused by many conditions such as the eastward movement of the plateau trough, the southward invasion of cold air, the low-level jet and the low-level shear line, which was under the circulation background of two troughs and one ridge in the middle and high latitudes and the stable circulation situation of the subtropical high. The unstable energy transported by the southerly warm and humid air flow provided the necessary energy conditions for the occurrence of the rainstorm. The forecast of the height field was consistent with the actual situation, and the forecast effect was good.