A one-dimensional mathematical model is developed to predict the re-melting and resolidification procedure during the transient liquid phase (TLP) diffusion bonding process for Al-Mg alloy. The macroscopic solute diffusion in the liquid and the solid as well as for the solid transformation to the liquid due to the solute macrosegregation are considered in this study. The effects of holding temperatures and the holding time on re-melting layer and the mushy zone thickness of the TLP diffusion bonding process are investigated. It is shown numerically that the holding time and the holding temperature influence the solute distribution strongly, which in turn influence the mushy zone thickness significantly.