Radiative transfer through participating gases can be accurately computed by a Line-by-Line (LBL) analysis. However, this method requires long computational time. Statistical Narrow-Band (SNB) model is used to estimate the spectral correlations for the gases and to evaluate the transmissivities and emissivities more rapidly and efficiently than the LBL approach. The spectral and total transmissivities and emissivities of CO2 gas, H 2O gas and CO2-H2O gas mixture are calculated by the SNB model in the wavelength range from 1.08 to 66.7 μn and in the temperature range from 300 to 2800 K. These values are in good agreement with those by the LBL calculations in the low temperature range and with Leckner's chart and Schmidt's experimental data rather than with Hottel's chart. The total emissivities of gas mixtures with different composition are also calculated by the SNB model and the spectral overlap corrections of the emissivities are compared with the existing results.