Abstract: CNx/SiC bilayer films (SiC as interlayer) were prepared on AZ91D Mg alloy surface by using magnetron sputtering technique at room temperature. The interfacial bonding, friction and wear properties as well as mechanical properties of the film were investigated. The results show that the surface particles of CNx/SiC bilayer films were closely combination, the SiC interlayer had good combination with the substrate and the CNx layer, which had gradient elements diffusion and the adhension force was larger than 12 N. The CNx films had low nano-hardness of 3.85 GPa, low elastic modulus of 30.46 GPa, high ratio of hardness and elastic modulus of 0.126 and good friction and wear properties. The friction coefficient of the film was about 0.19 when using Si3N4 balls as friction pairs under dry friction condition at room temperature, and the wear rate was 4.89×10-6 mm3·m-1·N-1.