Abstract: The Fengyun-3D satellite (FY-3D) Microwave Humidity Sounder (MWHS-II) successfully monitored the Typhoon “YAGI” (2411). In this paper, a three-dimensional variational assimilation framework of FY-3D MWHS-II data in clear sky is constructed in WRFDA. By setting up a single-band and dual-band joint assimilation and prediction experiment scheme of 118 GHz and 183 GHz, the microwave data assimilation and the forecast effect on the intensity, path and precipitation of Typhoon “YAGI” are systematically evaluated. The experiment shows that the assimilation of FY-3D MWHS-II data effectively improves the quality of the analysis field, and also has a positive impact on the forecast of typhoon intensity, track and precipitation. For the typhoon forecast, the assimilation of 118 GHz and 183 GHz channels improved the typhoon path forecast by 17.18% and 13.39% respectively, and the assimilation of 183 GHz in the ocean area made the path forecast improve by 14.59%. For the precipitation forecast, the assimilation of MWHS-II data significantly improves the hit rate of medium and small rainfall levels (< 25 mm) in the initial 24 hours, among which the 118GHz channel has a unique advantage in forecasting heavy rainfall (> 50 mm); The improvement effect of 183 GHz channel gradually appeared after 24 hours, while the dual-band joint scheme showed comprehensive advantages, and the FSS score of precipitation in each magnitude was significantly improved compared with the control experiment. The differential improvement effect of FY-3D MWHS-II’s 118 GHz and 183 GHz frequency bands on different forecast elements highlights the unique application value and potential of FY-3 MWHS-II data in regional typhoon numerical forecast.