Abstract: This research is about the thickness and optical thickness for the main wavelength of reflected light district location and transmission， to the two-component multi-layer composite film. Research shows that: two-component multi-layer films mainly reflected wavelength range is mainly determined by the optical thickness， little to do with the whole thickness; Along with the increase in optical thickness， mainly reflecting light wavelength is moving from the shorter position gradually to the region longer regional migration; the thickness of the multi-layer film whose reflective peak is in Near-infrared is about 35μm～70 μm. Through studies， the optical thickness with the main reflective wavelength relations has basically be found.

Key words: infrared reflectance film, Near-infrared, composite membranes