The spectral sensitivities of FY-4A/GIIRS （Geosynchronous Interferometric Infrared Sounder） in various atmospheric conditions are analyzed using Line-By-Line Radiative Transfer Model （LBLRTM）. On that basis, the information contents of temperature, humidity and ozone in FY-4A/GIIRS are measured by Entropy Reduction （ER） and the Degrees of Freedom for Signal （DFS）, which could evaluate the retrieve capabilities for atmosphere parameters of FY-4A/GIIRS. The results are shown as follows: （1） The sensitivity of temperature and humidity in long wave band of GIIRS are both varied with atmosphere condition, while there is little difference in the sensitivity of ozone under different atmospheric conditions. （2） The application potential for FY-4A/GIIRS with temperature, humidity and ozone profiles inversion is preliminary revealed. Therefore, temperature information content of FY-4A/GIIRS is the largest, followed by humidity under the US Standard atmosphere. （3） The information content of temperature and water vapor in tropical atmosphere is bigger than middle latitude atmosphere.