The fast radiative transmission model can quickly calculate the transmittances coefficients by extending a series of optical depth core functions and channel spectral characteristics, so as to obtain an accuracy that is compatible with the line-by-line model. In this paper, four fast forward operators are established to predict the optical depth ( OD) of mixed gas, water vapor line absorption and water vapor continuum absorption of RTTOV v7, v8, v9 and CRTM v2. 1 in 6 infrared channels of AGRI in FY-4. The largest STDs of all the four fast operators are less than 0. 6 K in brightness temperature of AGRI. The STD of water vapor, CO2 and channel transmittances simulation in RTTOV v9 are the smallest among the four models. And the errors are less in lower levels than that of higher levels in the channel transmittances simulation. Experiments were also conducted using standard atmospheric profiles to calculate the Jacobine and OD of the mixed gas, water vapor absorption and water vapor continuum absorption. The OD errors of the mixed gas decrease with the new information of the deviations of real atmosphere profiles and the reference ones in v9. Simulations of OD of water vapor are improved by 19 water vapor line absorption profiles and 4 water vapor continuum absorption ones in v9.