Abstract: Based on the WRF model and WRFDA assimilation system, the numerical simulation of the Southwest China Vortex (SWCV)-induced rainstorm process in Sichuan Basin on June 4th, 2019 was carried out by assimilating FY3C Microwave Humidity Sensor-2 (MWHS-2). The results show that the WRF model successfully predicts this heavy rainstorm, and the relative humidity (RH) of the mid-east Sichuan Basin in the model initial field is largely adjusted by assimilating MWHS-2 data. The assimilated precipitation in the Basin is closer to the ground truth than the unassimilated simulation. It not only improved the gap between the simulation path of 700hPa vortex and the actual path, but also improved the false activity path of 850hPa southwest vortex in the eastern basin in the simulation results. In the whole process, the water vapor convergence zones correspond well with the heavy rainfall zones, which mainly occur near the area where the southeastern flank of the 700hPa vortex’s cyclonic curvature reaching maximum overlaps the southern flank of the 850hPa vortex’s shearing.