Based on the spectral characteristics of the InfraRed Atmospheric Sounder (IRAS) channel, an atmospheric radiative transfer model for IRAS is developed. Using the HIgh resolution TRANsmission（HITRAN）2004 molecular spectroscopic database, the sensitivity to changes in atmospheric CO2 concentration of the measured radiance for ten channels of IRAS during the CO2 absorption bands were calculated to explore the feasibility of monitoring atmospheric CO2 concentration from Fengyun-3 (FY-3) meteorological satellite, and the uncertainties due to the errors of the atmospheric temperature, water vapor, and minor constituent concentrations were compared. It shows that the channel number 4 is the first choice to monitor atmospheric CO2 concentrations, and the ability to identify the changes in CO2 concentration is about 10×10-6 for the currently planned instrument noise.