Abstract: The development and system composition of a fever-screening thermograph and the basic principle of a thermal imager's temperature measurement are introduced. It is observed that the thermal imager's internal radiation clearly influences the accuracy of the temperature measurement. This paper introduces an evaluation model for the temperature measurement accuracy of a fever-screening thermograph and its main parameters. By analyzing the relationship between these parameters and the thermal imager noise, the blackbody reference source, and the environment, the temporal and spatial low-frequency noise of the thermal imager are found to be the key factors affecting the accuracy of the temperature measurement. Moreover, the influence of temporal low-frequency noise can be eliminated using a blackbody reference source, and the influence of spatial low-frequency noise can be eliminated using the two-point correction method based on an external shutter. Thus, the fever-screening thermograph can meet the accuracy requirements of human body temperature measurement.