The work aims to enhance surface strength of 9Cr18 steel by preparing fullerene-like CNx films on the steel. The films were prepared by adopting applying DC magnetron sputtering technique to sputter target C in mixed Ar and N2 gas at 300 ℃. Microstructures of the CNx films were studied with XPS, Raman spectra and SEM, and mechanical property and tribological property of the films was studied with nanoindentor and ball-on-disk friction testing machine, respectively. There were sp2 C—C, sp2 N—C and sp3 C—N chemical bonds in the fullerene-like films. Peak G of the films shifted toward lower peaks due to higher ID/IG ratio. With N2 flow rate increased, hardness and elastic recovery coefficient first increased and then decreased. The higher the hardness and elastic recovery coefficient were, the lower the wear rate was. The CNx films prepared at N2 flow rate of 10 mL/min feature in higher hardness and elastic recovery coefficient, and lower friction coefficient and wear rate. Surface strength can be significiantly increased by preparing fullerene-like CNx films on the surface of 9Cr18 steel.