Multispectral imaging technology for air to air missile is discussed in this paper.The design methods of co!optics and slit multispectral optical system are introduced. The key technologies of infrared multispectral guiding technology, such as band subdivision, multispectral infrared detector, system matching, multisensor signal fusion and spectral feature extraction are analyzed. An example of the air to air missile is given and a dual band infrared imaging detection using co!optics!light!path is realized. The target tracking based on spectral characteristics is conducted in allusion to IR decoys countermeasure.Experimental results show that the target recognition and disturbing restraint of the system is superior to signal band imaging guiding head.