Abstract: Aiming at the problem that thermal imager of existing in-service equipment cannot obtain target radiation temperature information, a simple measurement method for obtaining target infrared radiation characteristics using video images of thermal imagers is studied. By setting the gain and the level parameters in fixed integration time of thermal imager, the gray images of the blackbody at different temperatures are collected, and the gray and temperature models of the thermal imager are established. After collecting the target image, the target radiation temperature is retrieved by the model, and the target temperature is displayed in pseudo color. According to the target radiation temperature, the infrared radiation information such as target radiation brightness and radiation intensity can be calculated accordingly. The feasibility of this method is verified in the thermal imager experiment. The results show that the absolute error of retrieving the target radiation temperature is less than 4℃ and the relative error is less than 14% under the condition of certain gain and level. The error of target radiation temperature is large in field experiment. The model needs to be further improved. However, this method is feasible and has a strong application prospect.