Abstract: Infrared radiation thermometry is a noncontact temperature measurement technique that determines the temperature of a subject or specimen by detecting electromagnetic radiation within a specific spectral band. The signal received by the detector consists not only of the intrinsic radiation emitted by the target but also of the background infrared radiation reflected from the surface of the target surface. Based on Planck's law of blackbody radiation, we conducted a simulation analysis of the coupled influence of a high-temperature background and target emissivity on measurement errors in infrared thermometry. The results show that the combination of low target temperature, low emissivity, and high background radiation constitutes the most error-prone scenario. To address this, we proposed a correction coefficient retrieval strategy based on the Monte Carlo method, which enables unified modeling and compensation of complex background radiation effects. The proposed method is validated through calibration experiments using a standard blackbody furnace and industrial steel billet temperature measurements. The experimental results demonstrate that the approach suppressed the systematic errors induced by background reflection effectively and maintained a relative temperature measurement error within 0.5%. Thus, the proposed method can significantly enhance the accuracy and robustness of infrared thermometry systems under complex thermal radiation conditions.