Human target detection application systems for intelligent monitoring, assisted driving, etc. are often constructed by combining thermal imaging and visible light imaging technologies, which can significantly enhance system performance while achieving all-weather visual perception. This is because thermal imaging has a long operating distance and strong anti-interference ability, and can overcome some visual obstacles to find the target, but there are problems such as insignificant details and poor imaging effect; while visible light imaging has rich color and texture details , which can reflect the real situation of the scene, but is easily affected by lighting, occlusion, and shadows. The fusion of the two can play a good complementary role. Considering the importance of fusion of thermal infrared images and visible light images to this kind of all-weather human detection application system, this section discusses the fusion methods of these two types of images.