The CNx films with different nitrogen contents were prepared on single crystal Si(100) substrate under different nitrogen flow rates by pulsed bias arc ion plating. The surface morphology,composition,structure and properties of CNx films are investigated by optical microscope (OM),X-ray photoelectron spectroscopy(XPS), X-ray diffraction(XRD),Raman spectra and Nano-indentation, respectively. The results show that the surface of the films is uniform,smooth and dense. The nitrogen content in the CNx films decreases with the nitrogen flow rate decreasing. The results indicate that the deposited films are amorphous and have the typical characteristic of diamond-like carbon films. As the nitrogen content decreases from 18.9% to 5.3%, the hardness and elastic modulus of the films increase monotonically to a large extent, of which the hardness increases twice from 15.0 to 30.0 GPa. The sp3 content in the CNx films can be sensitively adjusted by controlling the nitrogen flow rate, leading to the changes of hardness and elastic modulus in large ranges.