Metal/ceramic interfaces have wide applications and the interface fracture plays an important role in determining mechanical behaviors of related structures. The cohesive zone model is widely used to modelling the crack opening and extension, especially used to modelling the interface crack. Although this model is widely used, it is a macroscopic phenomenological model, and its atomistic scale mechanism attracts great attention. In this paper an interface atomistic model of Ag/MgO is used to study the microscopic interface opening mode and some interesting results are discovered. By considering all atomic interaction potentials related to the interfacial structure in the molecular mechanics calculation, the interface tension stress-displacement curves for several interface structures with different sizes are simulated, and fracture properties upon displacing Ag and MgO adjacent to the interface are revealed based on the simulation results and by developing a series model on interface fracture properties. The results indicate that the interface fracture strength is independent of the size of interface structures for ideal interfaces, the total tension displacement of interface structures increases and the fracture appears catastrophic characteristic with increasing unit thickness, which is explained well by the series model. Furthermore, the interface separation behaviors of interfaces with the atomic vacancy and dislocations are simulated, the study indicates that the interface strength decreases for the interfaces with defects, and the defects decrease the catastrophic tendency. (C) 2017 Elsevier B. V. All rights reserved.