With double-layer structure thermal barrier coatings(TBCs) as the research object, three dimensional(3D) structure characteristics of TBCs such as morphology, composition, thickness, pores and porosity were researched by 3D X-ray microscopy and image processing technique. High resolution CT images of layered structure TBCs were reconstructed by 3D imaging method, 3D morphology of ceramic topcoat, bond coat and substrate were obtained by 3D segmentation and extraction, quantitative analysis of the important characterization parameters of TBCs such as thickness, pore size, pore number and porosity was performed. The results showed that the thickness of TBCs by 3D X-ray microscopy was basically consistent with the results of SEM, and the porosity was affected by the accuracy of the reconstruction.