ABSTRACT High‐temperature‐resistant and radar/infrared‐compatible stealth coatings (HRISCs) face severe spallation under extreme service environments. Focusing on the edge delamination failure mode of an HRISC subjected to 1150°C cyclic thermal and isothermal loads, a coating interfacial damage characterization method based on room‐temperature quasi‐static three‐point bending tests was developed. Based on the edge delamination theory, a critical strain–interfacial damage functional relationship was derived. Subsequently, the critical strain at the moment of interfacial crack propagation under bending load was acquired using digital image correlation (DIC) technology, enabling the characterization of interfacial damage in HRISC after different heat treatments. The results demonstrated that the damage at the dielectric/thermal barrier ceramic interface comprised both sintering‐induced and cyclic thermal–induced components. By linearly superposing these two, a damage model accounting for diverse dwell time conditions was established, achieving prediction accuracy within ±10% error.