In this paper, the experimental procedures are presented for carburizing and boronizing the 20 steel surface using a CW CO2 laser with an output power of 500-2000 W modulated CW. We also give a comprehensive analysis about the phase structure, the phase morphology, the distribution profile of the hardness and the resistance to abrassion of the sample after laser treatment. The experimental results indicate that the microstructure, the mechanical properties and the chemical composition in the surface layer of material will basically change. Furthermore, a preliminary discussion of the strengthening mechanism of the penetrating element by laser irradiation is also presented.