The surface absorption loss of an optical component is an important index used to measure its optical performance. The attachment of pollutant particles usually causes a significant increase in the surface absorption loss of an optical component. This study used the temperature rise detection method of an infrared thermal imager to investigate the influence of several typical pollution particles on the surface absorption loss of a highly reflective mirror. Stepped and discrete distribution absorption models were established based on the distribution characteristics of these pollutant particles. Considering that the temperature measurement accuracy was affected by the spatial resolution of the infrared thermal imager, the temperature rise data for a single pixel were extracted for a finite element analysis, and the local absorption loss on the surface of the coated element with an accuracy equivalent to that of a single pixel was obtained. Microscopy scanning results were used to further optimize the simulation model and obtain the absorption loss of particulate pollutants on the surface of a thin film element.