Large thickness ratio Al/Mg/Al laminates with the initial thickness ratio (ITR, the ratio of initial thickness of a single Mg layer to initial thickness of a single Al layer) ranging from 5 to 40 were prepared by hot rolling. The effects of ITR on the stress and strain fields, microstructure evolution and properties of Al/Mg/Al laminates were investigated by means of simulations and experiments. The results show that with increasing ITR, the ultimate tensile strength and yield strength of the laminates increase, while the interfacial bonding strength and elongation increase first and then decrease, and reach their maximum values of 12.3 N/mm (peel strength) and 23.32%, respectively, when the ITR is 20. At this time, the laminates have the best comprehensive mechanical properties, the deformation coordination ability between component metals is the best, and the texture on the Al side changes to shear texture. After the ITR reaches 40, the bonding performance of the laminates decreases, and the performance of the magnesium alloy is dominant.