In order to simulate the equivalent radiation environment of target and interference in the IR guidance process, and compare the effect of differences in target thermometry between monochromatic thermometry and chromatic thermometry under complex environment, the target and interference on space 6 km is simulated using IR dual color composite simulation system. Through the IR thermal imager calibrated accurately, the target and interference at different temperatures is tested using two methods of temperature measurement-monochromatic thermometry and chromatic thermometry. Blackbody temperature is measured by calibrated MW thermal imager and calibrated LW thermal imager, in the range from 25 ℃ to 40 ℃ of Blackbody temperature, the absolute error limit of LW thermal imager is 0.5 ℃, and in the range from 50 ℃ to 120 ℃ of Blackbody temperature, the absolute error limit of MW thermal imager is 0.2 ℃. When the target temperature is 500 ℃ and the interference temperature is 1000℃, the temperatures of target measured with LWIR, MWIR and chromatic thermometry are 28.5 ℃, 148.3 ℃ and 322.4 ℃, and the temperatures of interference are 56.7 ℃, 223.2 ℃ and 660.1 ℃ respectively. The experiment result indicates that the characteristics of target temperature can be better reflected using chromatic thermometry than monochromatic thermometry under complex environment.