Abstract: In order to explain the failure mechanism of thermal barrier coatings in aeroengine, considering the difference of 3 dimension interface topography unit and size, the distribution of thermal stress σ_yy in aeroengine thermal barrier coatings was calculated using ABAQUS finite element analysis. The calculating result shows that the stress is affected by interface topography unit obviously. Compressive stress exists in concave tomography unit and tensile stress in convex topography unit. Stress concentrates on boundary of topography point and reaches maximal value at lowest and highest place of concave and convex topography respectively. Compressive and tensile stress changes with the size of topography unit distinctly. The value of stress in danger point becomes larger with the increase of the length. Stress concentrates when the change of curvature is obvious and increases with the increase of curvature.