Characteristics of Cu3N thin films after deposition and 8 months after deposition are studied and compared experimentally. Films were produced by reactive magnetron sputtering mechanism and have been stayed in natural condition at room temperature for 8 months. It is observed that copper nitride thin films with conical microstructures on surface are oxidized while films with nodule like microstructures on surface are remained unchanged. X-ray spectrum shows that some nitrogen atoms of N-rich planes at Cu3N films are substituted by oxygen atoms after 8 months. The root mean square (RMS) roughness and sheet resistance of samples are increased significantly. The amount of oxygen in the structure of copper oxynitride thin films leads to increasing their band gap energy. It is found that the surface morphology is the most important parameter in stability of Cu3N thin film in natural condition.