The metal nanoparticles dispersed in matrices of composite material are able to apply in different technologies based on their peculiarity. This article reports the preparation of Ag/epoxy nanocomposite film with aligned Ag nanowires coated on glass substrate by multistep processing including synthesis of Ag nanowires by seed-mediated method, dispersion of Ag nanowires in the epoxy resin, and stretching to form the Ag/epoxy nanocomposite film. The results showed that Ag nanowires had been well aligned in the direction of stretching, both in the surface layer and in the internal of the film. Meanwhile, the Ag/epoxy nanocomposite film showed an obviously infrared polarization property in a broad wavelength range from 1600 to 2600 nm, with transmittance over 70%. The mechanisms for the orientation of Ag nanowires and the generation of polarization property of the films were discussed, respectively.