In recent years, infrared imaging technology has developed rapidly in China. According to the operating temperature, Infrared Focal Plane Arrays (IRFPAs) can be divided into cooled ones and uncooled ones. IRFPAs have the advantages of high sensitivity, high accuracy and excellent performance, but they are expensive. So they are mainly used in the military field now. In the use of a certain cooled infrared thermal imager, if the temperature of the scene changes greatly or if the imager operates at an extreme ambient temperature, a phenomenon may occur, that is, the image may exhibit white in the middle and exhibit black in the corner or vice versa when integration time is adjusted. Firstly, infrared image data are collected at different blackbody temperatures in different integration time. Let the phenomenon be recurrent according to the above problem. Then, the root of the problem is analyzed and the solution is put forward according to the principle of two-point correction. Finally, the correctness of the method is verified by the experimental data and the solutions to the problem are summarized.