The geostationary orbit microwave sounding satellite carrying a microwave sounder utilizes the relatively stationary characteristics of the platform, as well as the microwave"s ability to penetrate clouds and rain, to achieve high-frequency, all-day, and all-weather observations of the atmosphere, providing high-value data for numerical weather forecasting and disaster weather research. This paper analyzes the sounding capability of the Chinese FengYun-4 geostationary orbit microwave satellite currently under development. The observation method and product system are introduced. Its millimeter wave sub-millimeter wave sounder has added the 55 GHz microwave hyperspectral frequency band and 380-425 GHz terahertz channel that are not available on existing low orbit satellites, greatly expanding the sounder"s ability to observe atmospheric status and cloud parameters. The unique observation geometry characteristics of the satellite are shown through simulation technology. Based on the ARMS fast mode and atmospheric backgrounds, the brightness temperature of typical channels for detection of temperature and humidity, as well as the terahertz channels, are simulated under typhoon background.