The design of the cooled infrared system can not avoid the problem of cold reflection, so it is necessary to complicate the optical system to weaken the influence of cold reflection. By analyzing the cold reflection characteristics of the cooled infrared system, the differential threshold cold reflection correction method is proposed, which can relax the restrictions on the cold reflection in the optical design stage, without considering the cold reflection. After the system is optimized, ray tracing is carried out to simulate the cold reflection phenomenon in the real scene, and then the cold reflection is eliminated by this method. A cooled infrared optical system is designed. After using this method, the image is clear subjectively, and many image quality evaluation functions are improved objectively. The results show that this method can effectively reduce the cold reflection of the cooled infrared system, simplify the design of the optical system, and is of great significance to the miniaturization and lightweight of the system.