To investigate the influences of the coating thickness and interlayer-to-top layer coating thickness ratio tint:ttop on the interface stress in the TiN-interlayer coating/ substrate under contact stress. Methods Using Finite element method, the Mises stress gradient and the maximum shear stress at one interface between the coating and the base and the other between the top layer coating and the interlayer coating were studied. Results The coating thickness t and the interlayer-to-top layer coating thickness ratio tint ： ttop had little influence on the interface stress between the coating and the base,however, they showed obvious influence on the interface stress between the top layer and the interlayer coating. For the thin coating, the Mises stress gradient and the maximum shear stress at the interface between the top layer and the interlayer were decreased when the interlayer-to-top layer coating thickness ratio tint ： ttop increased, while for the thick coating, the Mises stress gradient and the maximum shear stress at the interface between the top layer and the interlayer were increased when the interlayer-to-top layer coating thickness ratio tint ： ttop decreased. For the same interlayer-to-top layer coating thickness ratio tint:ttop, the Mises stress gradient and the maximum shear stress were first increased and then decreased when the coating thickness increased. Conclusion The coating thickness and the thickness ratio showed distinct influences on the interface stress of a double coating system.