Amorphous carbon nitride thin films were prepared in $N_2-H_2;and;N_2-He$ plasmas by arc ion plating(AIP) method. X-ray photoelectron spectroscopy(XPS) study revealed that nitrogen atoms were bonded with carbon atoms as the forms of $C{equiv}N$, C=N and C - N(not reliable) in the films. The decrease in $N_2$ partial pressure led N/C atomic ratio to be reduced from 0.3 to 0.1 because of the loss of reactive nitrogen in the systme. In the $N_2-H_2$ system, the component of the C=N bonding became predominant with the decrease in the $N_2$ partial pressure because hydrogen atoms terminated $sp^3$-carbon$ dangling bonds and nitrogen atoms were linked to carbon atoms located $sp^2$ sites.