Abstract: The research on digital modeling of heat air reflow soldering process is of great significance for obtaining the temperature distribution of PCB assembly, revealing the heat transfer mechanism in the soldering process of PCB assembly,and promoting the digital development of heat air reflow soldering process. A digital modeling method for heat air reflow soldering process was proposed. The process of PCB assembly being transported by conveyor belt was simulated by using the dynamic mesh method, and the automatic simulation flow of the whole process was established. The results show that the PCB assembly is welded by convection heat transfer, and the distribution density and position of the assembly on the PCB assembly affect the heat transfer efficiency of the PCB. Through the analysis of the temperature change of the connection structure of the solder ball and pin, it is found that the substandard soldering temperature of the device in the form of the ball grid array package is more likely to occur in the process of heat air reflow soldering.