BCN films were prepared with unbalanced magnetron sputtering boron carbide film followed by nitrogen plasma-based ion implantation at different voltages on Si substrate. The implantation voltages vary from 10 kV to 50 kV. The chemical states of B, C and N of the films were studied with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The nano-hardness and elastic modulus of films were measured by Nano-Indenter. The results showed that amorphous BCN films formed in the nitrogen implanted layer. The amorphous peak becomes obvious with increasing of the implanted voltage when the voltage is under of 40 kV. The Nano-Indenter measurement showed that the B-C bond content and the disorder degree affect the hardness and modulus.