The work aims to increase the bonding strength of the CrC thin films by improving the preparation process of the films. Gradient Cr/CrC films were deposited on M42 high-speed steel by RF enhanced magnetron sputtering with Cr and graphite as targets and C2H2 as reaction gas. Microstructure, composition and bond structure of thin film were analyzed by SEM, EDS and Raman spectroscopy. Adhesion strength was evaluated by nano-indender and Rockwell-C hardness tester. A dense and uniform gradient Cr/CrC film was deposited through the experiment. The bonding strength and the sp3 content in the films increased first, and then decreased with the increase of RF power of graphite target. When the RF power was 250 W, the film had the highest sp3 content and the maximum hardness of 21 GPa. The pure Cr transition layer can effectively absorb the internal stress in the film, improve the film/substrate bonding performance, and significantly enhance the bonding strength of the Cr/CrC film. The RF power of graphite target has a significant effect on the structure and bonding strength of gradient Cr/CrC film. The film has the highest hardness and bonding strength when the RF power is 250 W.