This article developed an analytical two-color thermometry model combined with a mathematical radiative heat transfer model. The proposed model was used to investigate the performance of two-color pyrometry affected by absorption bands in hot combustion gases. This model was validated by comparing with a range of measured data and the results of other numerical solutions. The analysis of the temperature errors produced by a high-temperature H2O-CO2-N-2 mixture in three measurement situations was presented. The presence of the high-temperature H2O-CO2-N-2 mixture greatly affected the measurement accuracy of two-color pyrometry. Minimizing the absorption and emission effects by selection of the instrument spectral band is useful when interfering combustion gases are at low concentrations. The results showed that the measured temperature had an apparent oscillatory phenomenon due to combustion gases' absorption and emission effects. This phenomenon tended to further strengthen with a thicker hot interfering gas layer. Through an analysis of the mechanism of the oscillatory behavior, we presented a correction strategy to minimize the temperature error. Theoretical temperature shifts at some selected wavelength pairs produced by changes in the model input parameters were estimated to provide at least a basis for an uncertainty analysis, and a sensitivity analysis of the impact factors was performed. The calculated temperature error was nearly exponentially increased with an increase of the combustion gas temperature when the gas temperature was greater than the target temperature, and it was linearly increased in magnitude with an increase in both the gas mixture concentration and viewing path length. The analyses presented in the article may provide valuable descriptions of measurement errors produced by combustion gases and necessary theoretical supports for the design and application of a two-color pyrometer in the presence of combustion gases.