Cubic-C3N4 nanoparticles were synthesized in CNx/TiNx multilayer films by a nitrogen ion beam sputtering in situ titanium and graphite targets alternatively. The C-N bonding states within the CNx layers, the morphologies and structure of compounds in the films have been investigated by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. Two types of bonding states, N-sp(2)C and N-sp(3)C, exist predominantly in the CNx layer, and crystalline particles with sizes of 10-60 nm were observed in the CNx layer of the films. Their diffraction data can be assigned to the cubic-C3N4 structure.