With the development of high resolution cooled infrared thermal imager, the frequency of analog signal has been improved. This leads to the need to ensure the quality of analog signals along the transmission path, so as to ensure the imaging quality of infrared images. In the imaging experiment of 1280×1024@15 m medium-wave thermal imager, it is found that the highlighted point source objects in infrared images appear in pairs. It means that the ghosting appears. This causes serious interference to the detection and identification of smaller targets. In this paper, the simulation signal transmission path model and the simulation circuit signal are extracted and the infrared images are further compared. It is found that the impedance mismatch on the signal transmission path is the main cause of image ghosting, and it is verified that when the matching resistance on the transmission path is between 40 Ω and 70 Ω, the signal transmission quality is better, and the infrared image ghosting problem can be solved.