Abstract: The cubic boron nitride (c-BN) thin films were deposited on p-type Si (100) substrates by means of radio frequency sputtering. The films were characterized by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) spectra. The results indicate that the working gaspressure is the important factor for preparing cubic boron nitride thin films. In order to obtain cubic boron nitride thin films the working gas pressure must be appropriate, otherwise the cubic phase can not be synthesized. At 0.67 Pa of working gas pressure, the cubic boron nitride thin films that contain 92% cubic phase content can be successfully synthesized.