In order to solve the problem of the existing single waveband thermal imaging system can’t get precise temperature of object with emissivity unknown, an optical system of beam splitting lens and filter were used to established a colorimetric temperature measurement system based on infrared thermal imaging system. Completed the compensation for non-effective pixel, enhancement of contrast, calibration of nonhomogeneity and coherence for infrared thermal imaging system according to the application requirement, then acquired the calibration data with blackbody as radiation source at 200°~500° and fit it. A temperature measurement test performed at last, compared with the result acquired by thermocouple and single waveband thermal imaging system, it was shown that the colorimetric pyrometry system achieve the attractive precision after calibration and applied to measure the temperature of the object with emissivity unknown.