We have studied the influence of nitrogen on the chemical properties of the hydrogenated carbon nitride (a-CNx:H) film deposited by CH4/N-2 dielectric barrier discharge (DBD) plasma. X-ray photoelectron spectroscopy (XPS) indicates that carbon and nitrogen form an unpolarized covalent bond in these C-N-x materials, and the observed chemical shift in the C 1s and N 1s binding energy is explained with respect to N Is incorporation. Furthermore, the average nitrogen content (N/C approximate to 0.76) in the films was systematically varied by changing the nitrogen partial pressure (CH4/N-2 approximate to from 5:1 to 1:7) which is well supported by the elemental analysis. Fourier transform infrared (FTIR) absorption spectra exhibit significant changes in different C-N, C N, and NH/OH molecular bands at higher nitrogen concentration in the film. The isonitrile and nitrile groups (-NC and -CN) are increased with the increase of deposition time. In addition, the elemental analysis, proton NMR, and thermolysis mass spectrum show that the composition of the film with the ratio CH4/N-2 approximate to 1:1 is C, 67.68; H, 9.88; N, 16.53 (in wt %) and that the film is composed of polymers, probably containing linear chains which are cleaved off on heating in vacuum,