The influence of laser selective melting parameters on the thermal physical process is analyzed by establishing a mathematical model. Taking moving Gaussian heat source as fixed heat source, a laser selective melting heat source model is established, and based on this, the heat transfer control equation is designed. By dealing with the latent heat of phase change in the governing equation, the phase change process of the thermal physical process of the material is analyzed. The thermal property parameters of materials were analyzed by setting global variables. Based on heat source model, governing equation, latent heat treatment of phase transition and thermal property parameter analysis, a mathematical model of the influence of thermal physical process is established. The finite element method is used to solve the mathematical model and analyze the influence of laser melting parameters such as laser power and scanning rate on thermal physical processes such as temperature and molten pool size. The test results show that the laser power has a significant effect on the temperature field of thermal-physical process and the size of molten pool. Appropriately increasing the laser power will expand the maximum temperature distribution range of molten channel, reduce the spheroidization of molten channel, solve the problem of molten channel bending, increase the size of molten pool, and improve the quality of parts. The scanning rate also has a significant effect on the temperature field and the size of the molten pool. Properly reducing the scanning rate can increase the size of the molten pool and better control the thermal physical process. The influence of beam diameter on temperature field and molten pool size is small.