Abstract: By means of Monte Carlo (MC), the process of the nitrogen ion implanting in the titanium was simulated, which occurred during the nitriding titanium by laser and plasma nitriding (LPN). The nitrogen ion distribution in the titanium, the biggest penetration depth, and the thickness of the nitriding layer were calculated at different laser power density. Under the conditions, P 0 =1.0×106 W/cm2 (laser power density) and (scanning velocity), the simulated results were in good agreement with the corresponding experimental results. The simulations predicted that, when and 2.0×105 W/cm2 ≤ P 0 ≤1.0×106 W/cm2, the penetration depth increased with the laser power density increasing. A better nitriding effect could be obtained when the laser power density was higher than 8.0×105 W/cm2. [Copyright &y& Elsevier]