The　objective　of　this　study　is　to　investigate　feasibility　of　millimeter　wave　nondestructive　testing　to　detect　the　defects　of　TBCs　and　to　determine　sensitivity　of　detection　when　frequency　changed.　The　simulation　to　monitor　the　delamination　of　TBCs　and　TGO　are　carried　out　using　computer　simulation　technology-microwave　studio.　WR18　rectangular　waveguide　(40-50　GHz)　and　WR14　rectangular　waveguide　(50-60　GHz)　are　used　to　detect　the　delamination　of　TBCs.　The　depth　of　cracks　(parallel　to　the　interface　of　TC　and　BC),　the　size　of　the　shape　of　delimation,　the　thickness　of　delimation　are　studied.　Four　rectangular　waveguides,　including　WR42　(18-26.5　GHz),　WR28　(26.5-40　GHz),　WR18　(40-50　GHz)　and　WR14　(50-60　GHz),　are　used　to　detect　TGO.　The　changes　in　the　phase　of　reflection　coefficient　are　primarily　studied.　The　results　show　that　the　phase　difference　of　reflection　coefficients　can　represent　not　only?the　existence　of　the　defect,　but　also　the　depth　of　the　defect.　When　the　delamination　surface　is　less　than　the　aperture　of　the　waveguide　probe,　the　phase　of　reflection　coefficient　can　represent　the　size　of　delamination.　When　the　delamination　surface　is　more　than　the　aperture　of　the　waveguide　probe,　the　phase　of　reflection　coefficient　can　represent　the　thickness　of　delamination.　The　phase　difference　of　reflection　coefficient　can　represent　the　TGO　thickness.　Besides,　the　sensitivity　is　greater　in　high　frequency　than　low　frequency.　©　2013　Journal　of　Mechanical　Engineering.