Abstract: CN_x films have been prepared by DC magnetron sputtering of graphite in pure nitrogen atmosphere. N/C ratio is between 0.21 and 0.42, strongly correlating with deposition parameters. The hardness and modulus are related not only to the N/C ratio,but also to the formation and the amount of C≡N triple bonds in the CN_x films. High bias voltage and high sputtering power are beneficial to the increase of C≡N bands and so are helpful to increase the hardness and bulk modulus.