In view of the traditional infrared reconnaissance method existence insufficiency, integrated ultraviolet, infrared and visible light imaging advantages, system uses DSP as the processing core, build a small real-time image fusion system, through the optical structure design, after the rate adjustment and digital displacement, and a series of experiments are conducted to multispectral fusion. The experimental results show that the system design is reasonable, able to complete the multi-source image fusion. The system has these advantages of small volume, light weight, low power consumption, fast processing speed and working modes of optional features, very suitable for the loading ability is limited, to perform various tasks of UAV flight application.