Abstract: Ultra-thin films of about 1 μm are widely used in friction pairs with point/line-contact, and their interfacial failures have significant effects on the service life of frictional components. An interface mechanical model of film-substrate system with hard or soft thin films deposited on the bearing steel surfaces is built to analyze the interface stresses and deformations under the linear contact. Using image method of complex function, the solution of unit point force is obtained as the Green's function for evaluating and integrating. The model is verified as a degradation of homogeneous material. The distribution states of interface stresses for a cylindrical contact with DLC and MoS₂ of hard and soft films are calculated and discussed. This model can be used for interfacial analysis and design in the mechanical components with ultra-thin films.