Copper nitride thin films were prepared on silicon glass substrates by means of RF magnetron sputtering deposition, and then the effects of nitrogen partial pressure in a fixed-total N₂-Ar mixture sputtering gas flow on the preferential crystalline orientation, the size of surface grain and micro-mechanical properties were investigated. It is showed that when the nitrogen partial pressure is low, the nano-mechanical property of the thin film is poor. As nitrogen partial pressure improves the preferential orientation transforms from plane (111 ) to plane (100 ) , the crystalline grain size shrinks and the elastic modulus first increases but then decreases.