Abstract: To address the issue of stray radiation signals interfering with measurement accuracy in radiation thermometry of gas turbine combustors, a physical model was established that accounts for emissivity, high-temperature residual wall reflections, and high-temperature gas absorption/radiation. An error correction model for determining true temperatures was subsequently developed. Quantitative sensitivity indexes of model input parameters were analyzed across three distinct operational bands of an infrared thermal imager. Results show that even in spectral bands with high gas transmittance, gas influence remains non-negligible. Neglecting gas effects causes maximum relative errors of 9.7% and 5.5% for short-wave infrared (SWIR) and mid-wave infrared (MWIR) imagers, respectively. Sensitivity indexes of input parameters vary across operational bands. Parameters with lower sensitivity indexes can tolerate greater measurement uncertainties, whereas those with higher indexes require precise measurement.