In this paper, numericalsimulation for temperature field of Mo2/N films generated on molybdenum surfaceusing laser gas alloying(LGA) method is performed by finite-difference method. Thenumerical model used takes into account of Gauss distribution ‘ in space and time' of laser spot, the finite size ofsample, the temperature dependence of themophysical properties, and the surface heatlosses due to convection and radiation. The changes of temperature field are calculatedaccordingly. The feasibility of using pulse laser for laser surface transformationhardening and laser surface remelting is also analyzed.