Abstract: The pure titanium was nitrided by laser nitriding method in atmospheric ambient with the radiation of CW CO2 laser.The activated nitrogen beam was introduced into the melting pool together with the laser beam.The samples were tested with X-ray diffraction(XRD) method.The results show that the nitridation on the surface of titanium can be realized by choosing proper laser parameters,including laser power density,scanning speed and pre-heated treat ment to nitrogen gas.The minimum power density is 6.5×105W·cm-2 and the maximum scanning speed is 600mm·min-1.The distribution of temperatu refield during the nitriding process is simulated with semi-infinity model.From this model,the theoretical threshold of scanning speed is deduced to be 600mm ·min-1.This value is near to the experimental result.