Synchronous measurement of temperature and the deformation field can be achieved through reasonable assignment of R, G, and B channels of a CCD camera in a high-temperature environment. The R and G channels are used for colorimetric temperature measurement, and the B channel is adopted for deformation measurement. However, the external blue compensation light source may cause crosstalk of the R and G channels, leading to inaccurate measurement. To eliminate such an interference phenomenon, we first use the function relationship between the illumination of the object surface and the exposure time to calibrate the camera parameters at room temperature, thus removing the initial gray level of the R and G channels in the high-temperature image. This contributes to improving the low-temperature measurement accuracy for the temperature field, with a calculation error of <5  %  . In contrast, an experiment shows that the temperature deviation of the low-temperature region calculated using the uncorrected image is up to hundreds of degrees. Then, the radiation intensity of channel B is removed using the temperature balance relationship, which increases the calculation accuracy by 15% in comparison to the uncorrected result. The algorithm is validated by the heating experiment of C/SiC material with an oxy-acetylene flame. The results suggest that the proposed improved algorithm is of great significance for the evaluation of materials at high temperatures.