ABSTRACT Tailoring interface microstructure and improving mechanical behavior in brazing bonding heterogeneous materials and structures [1, 2] is crucial for various industrial applications. In order to improve the interlaminar mechanical properties of lightweight magnesium alloy-based fiber metal laminates (Mg-based FMLs) with heterostructures, a novel low-temperature Mg-Zn-Al brazing filler metal was first designed, and the reinforcing effects of the optimized solder alloy compositions and ultrasonic-assisted brazing process parameters on the interfacial diffusion and mechanical behavior of the Mg-Zn-Al/Mg brazing bonding were then investigated based on molecular dynamics (MD) simulation. The macro-level interlaminar fracture toughness of the adhesively bonded Mg-based FML specimens were finally tested to prove the effect of ultrasonic assisted soldering for enhanced adhesion. The results show that under the conditions of optimized low-temperature filler brazing metal and ultrasonic assisted brazing process parameters, the diffusion coefficient of Mg-Zn-Al/Mg interface increases by 5-10 times, the bonding layer thickness increases by 2.5-7.6 times. In terms of mechanical properties, the tensile strength of the ultrasonic assisted brazing interface is 11.5% higher than that of the high-temperature brazing interface, while the mode I and mode II values of Mg-based FMLs are increased by 180.7% and 7.9% respectively compared to those of the conventional resin bonding interfaces due to the formation of the dense interfacial microstructure and synergistic enhancements in the Mg-based FMLs. The research results provide a promising pathway for the integrated designing and manufacturing of high-strength and multifunctional hybrid structures.