The article deals with the mechanism of laser alloying of P6M5 steel and the character of its change. The results of studies of laser doping and a change in the results with varying parameters of laser radiation are proposed. Tungsten boride (W2B5) was used as a legrant. The authors spent an analytical assessment of the mixing mechanism in laser doping. It is noted that the research of this sphere do not have a systemic nature. Many authors who explore this problem, think that it is one of the main and most controversial in laser doping. Therefore, the results are got by different scientists cannot be systematized due to significant differences in the schemes and conditions of research. It is investigated the processes occurring during the formation of the structure of surface layers during laser doping. It is obtained optimum laser processing conditions. It is proved experimentally that the processing speed during laser alloying effects on the nature of the distribution of the legrant in the alloy bath and regulates the mixing mechanism, including both diffusion and convection.