The invention relates to a visible light image and infrared image fusion processing system and a fusion method. The fusion processing system comprises an image acquisition module, an image fusion module and an image display module, wherein the image fusion module is connected with the image acquisition module and the image display module. By adoption of the fusion method, the fusion ratio of a visible light image to an infrared image can be adjusted according to requirements, and detailed images are filtered and compared and then enhanced, so that detail information of a fused image is improved, and noise interference is avoided. Furthermore, fusion weights of the visible light image and the infrared image and the detail enhancement degree can be flexibly controlled through external parameter adjustment, and thus various display requirements are met.