The invention relates to a method for nitridizing the surfaces of titanium and titanium alloy, belonging to the technical field of preparing materials for metal surfaces and the technical field of processing the metal surfaces. The method uses pure N2 or the mixed gas of N2 and Ar as iron gas, uses plasma welding equipment to obtain nitrogen plasma flame, heats the surface of the titanium and thesurface of a basal body of the titanium alloy, controls the nitriding temperature and time, and partially forms nitride layers on the surface of the titanium and the surface of the basal body of the titanium alloy, thereby solving the problem of poor abrasive resistance of the surfaces of the titanium and the titanium alloy. Compared with the prior art, the processing method does not need complexand expensive equipment, can realize on-site operation in the air, has easy and flexible execution, can partially nitridize the basal body, and has short processing time.