Nano-scale metallic films have been proven to be effective infrared absorption layers for pyroelectric detectors operated at 14~16 μm spectral range for space applications. The infrared absorption improvement can be achieved by adjusting the thickness and surface characteristics of the nano-scale Nickel-chromium (NiCr) film deposited on the LT (lithium tantalite) crystal materials. By regulating the thickness of the crystal materials, the absorption wavelength is adjustable as well by changing the depth of the anti-reflection cavity. To enhance the infrared absorption further, chemical corrosion is applied on this film, which generates a rough nano-scale surface structure and greatly increases the absorption surface area. By combining these two methods, absorption at specified infrared wavelength could be distinctly enhanced, and the manufacturing process is fully compatible and easy to realize. Experiment results suggest that the absorption performance which could be controlled agrees well with the simulation and design.