The in-depth study for how the welding interface forms has great significance for the practice of welding engineering.The experiments, numerical simulations and analyses from the macro perspective have been widely carried out, and have made much progress.However, most studies focus on the theories of wave formation, bonding interface morphologies and mechanical properties of the materials joined by explosion welding, and the researches for diffusion at the bonding interface still remain experimental stage, mostly.In physical nature, the inter-diffusion of different kind of atoms at the bonding interface from two joining materials plays an important role in the explosion welding process.The mechanism of atomic diffusion in explosion welding process of bulk metallic glass (Ti40Zr25Cu12Ni3Be20) and crystal metal (aluminum 1060), and Cu and A1 are investigated through experiments and numerical simulations by a self-developed CE/SE hydrocode and molecular dynamics (MD).The diffusion near the interface of the weldment of Ti40Zr25Cu12Ni3Be20 and aluminum 1060 is presented by HRTEM (High-resolution transmission electron microscopy).Moreover, a Cu-A1 explosion welding model is established based on MD simulation to capture the atomic diffusion behavior in the welding process.Then the diffusion coefficient gotten from the simulations is used to calculate the thickness of some local areas in the diffusion layer, and the results and the corresponding experimental value fit very well.