<p>The static and dynamic performances of mechanical equipment are closely related to the contact surface’s contact condition. This research uses experimental measurements to observe the microstructure of microrough surfaces. Using this premise, it proposes a novel approach for calculating the contact stiffness of contact surfaces based on the observed interface microstructures and the distribution patterns of micro-convex bodies. This study divides the deformation of micro-convex bodies under load into three stages: elastic deformation stage, elastic-plastic deformation stage, and plastic deformation stage. A contact stiffness calculation model for interfaces is established based on the statistical theory of micro-convex bodies. The numerical simulations of this contact stiffness model of the interface revealed the nonlinear relationship between the contact load and the contact distance of the interface, as well as the effect of root mean square roughness a on the contact area. It also demonstrated the influence of contact distance on contact characteristics. The proposed contact model’s effectiveness was verified by its comparison with experimental results (experimental spring model, abbreviated as the spring model), Xiao Huifang’s modified experimental contact model, Kogut and Etsion’s statistical contact model, and Greenwood and Williamson’s model. The proposal of a rough interface’s contact stiffness calculation model in this research provides a reference for calculating the contact stiffness and performance prediction of mechanical contact interfaces.</p>