Abstract: The traditional studies about a mechanical interface were mostly based on the assumption that a smooth rigid plane contacts with an equivalent rough surface, which ignored the lateral contact and interaction between asperities, so there has a serious error in those theoretical models. Aimed at an interface bearing normal static and dynamic force, the energy dissipation was studied from a micro level, which considered the lateral contact and interaction between asperities. The normal force can be divided into a normal component of force and a tangential component of force. The relation between the normal component and the deformation, and the relation between the tangential component and the displacement can be gotten during loading/unloading in the elastic stage, elastic-plastic stage, and plastic stage, respectively. According to the composition of forces, the relation between the normal force and total deformation can be derived. Because of the plastic deformation and friction between asperities, the curves of the loading and the unloading not coincide, and there is a hysteresis loop. One cycle of energy dissipation can be calculated by integrating the area of the hysteresis loop, which includes the strain energy dissipation and the friction energy dissipation. The simulation analysis shows that:the energy dissipation nonlinear increases with the increase of the deformation. The bigger contact angles the more energy dissipation, and it's the most obvious in the elastic stage. There are only the friction energy dissipation in the elastic stage, so under the low loads must use the assumption of double rough surfaces. In the plastic stage, there are only the strain energy dissipation, and the effects of the contact angle on the energy dissipation are very little, so under the heavy loads can use the assumption of the single rough surface to study the mechanical interface. Comparing with the KE and Etsion models, our proposed model is well agreed with the Bartier's experiments.