The element diffusion process of the binary systems (Fe-Cu and Fe-Ni) in the vacuum brazing of high-nitrogen stainless steel with AgCuNi filler was investigated by Lammps software for molecular dynamics simulation analysis. Results show that the mutual diffusion phenomena of Fe-Cu and Fe-Ni binary systems are obvious, and the thickness of the diffusion layer is increased with increasing the diffusion time. In the Fe-Cu diffusion process, only the mutual atom diffusion occurs; whereas not only the mutual atom diffusion, but also the formation of mesophase occurs in the Fe-Ni diffusion process. In the Fe-Cu binary system, the mean square displacement (MSD) and diffusion coefficient of Fe atom are greater than those of Cu atom, so the diffusion ability of Fe atom is better than that of Cu atom. Similarly, in the Fe-Ni binary system, MSD and diffusion coefficient of Fe atom are greater than those of Ni atom, so the diffusion ability of Fe atom is also better than that of Ni atom. With increasing the diffusion temperature, MSD and diffusion coefficient of atoms are increased, and their diffusion ability is enhanced.