Abstract: The interface free energy density is an important quantity characterizing the mechanical property of interface in nanocomposite systems. In this paper, molecular dynamics simulation method is adopted to investigate the interface energy density of different FCC metallic bi-nano-scaled plates. The morphology of the interface crystal structure and the interface effect on the atomic potential are analyzed. It is found that interface atoms have periodically wrinkled rarefied or serried configurations, and the potential energy of interface atoms is also periodically distributed. The potential energy of atoms near the interface is obviously different from that of atoms inside the nano-plates. Both the Lagrange interface energy and the Eulerian one increase with the increase of the thickness of the bi-material, which approach the interface energy of a bulk bi-material finally.