Abstract: α-C: H films deposited on HgCdTe substrate material by using radio frequency plasma vapor deposition method have been analyzed by Raman spectroscopy, indicating both diamond like and diamond phases appear in these films. The results of analysing the interface of the DLC/HgCdTe by AES show that the outward diffusion of components of the substrate can be barred completely when the thickness of DLC film is more than 700A. The comparison of infrared transmittance spectrum between the HgCdTe wafer and the DLC/HgCdTe shows that the diamondlike film can improve the transmittance property of HgCdTe photoconductive devices obviously over a wide range of wavelength from 4 to 12μm. The maximum value of antireflectivity can reach 26%.