<p>The increase in the interfacial roughness of the thermal barrier coatings (TBCs) leads to the concentration of interfacial stresses, but the experimental life also increases. The intuitive explanation of this anomalous failure mechanism has been a problem that has plagued scholars for many years. In this study, a method for solving the interfacial morphology-dependent stress of TBCs is developed, and the anomalous failure mechanism is elucidated intuitively. In addition, the multiscale of TBCs with microstructures is established based on experimental parameters by applying the submodel method, and the effects of interface roughness on conventional stresses and morphology-dependent stress are analyzed. The results show that both the maximum principal stress and the equivalent stress increase with the increase in the interface roughness. As the roughness increases, the compressive stress perpendicular to the interface weakens and the minimum value of shear stress along the interface does not differ much. At the TBC interface near the valleys, cracks initiate under the minimum value of shear stress along the interface, and then, cracks expand under compressive stress perpendicular to the interface until the TBCs are disrupted. The strong correlation between compressive stress and damage at different roughnesses, as well as the fact that the damage location of the actual TBCs is consistent with the description of the failure mechanism, which justify the failure mechanism proposed in this study. These conclusions can provide a theoretical basis for the mesoscopic interface design of long service life TBCs.</p>