In colorimetric temperature measurement, high temperature background radiation interferes with the accurate measurement of target temperature. Monte Carlo method is used to simulate the emission position, radiation direction, reflection and absorption characteristics of background radiation by probability distribution. The radiant energy beam reflected by the target was detected by the detector and compared with the theoretical radiation difference to verify its accuracy. On this basis, a method that can eliminate the influence of high-temperature background radiation in a complex environment and improve the accuracy of temperature measurement is proposed.