In order to simulate the radiance of infrared and water vapor channels of FY2B with RTTOV, a multi-variables linear regression was used to produce transmittances by using spectral response functions of these channels and a precise transmittances database of 600 - 3000 cm^ - 1 generated from GENLN2 at 6 viewing angles. When the same atmospheric profile and the new coefficients were put into RTTOV, simulation of FY2B and GMS showed that similar channel radiances were obtained. The comparative analysis of the deviation between the simulated radiances obtained with the profiles from ECMWF model forecast and the new coefficients for FY2B in RTTOV and the real observation for infrared and water vapor channels of FY2B indicate that the satisfying precise of radiances can be obtained within very short time.