The invention discloses a double-spectrum night vision instrument vehicle-mounted system and a double-spectrum fusion design method. The system comprises an infrared double-spectrum imaging die set used for imaging of a visible spectrum and an infrared spectrum and for collection, processing, fusion and transmission of the image data, an image receiving system used for completing the receiving of the image data, a display terminal used for displaying the images for an observer, and a control terminal used for controlling the function and on-off of an imaging mode. Due to the adoption of the system and the method, the problem that coaxial imaging of the double spectrum image is slight bad is solved, the machining precision requirement of the imaging system is reduced, more clear images are provided for forward observation for a train; a fusion method based on a scene moving object provides a reference source for the double-spectrum imaging system, the computation load is reduced, the registering reliability is improved, the imaging on the hardware is convenient, and the real-time performance is possessed; a weight fusion method based on multi-scale bilateral filtering is simple and feasible, improves the imaging detail information and reduces the calculation ability.