In　order　to　ensure　thermal　insulation　performance　of　thermal　barrier　coating,　the　thickness　detection　of　thermal　barrier　coatings　was　carried　out　using　microwave.　R281A　rectangular　waveguide　is　used　as　the　probe　to　transmit　and　receive　microwave　signals　with　frequency　of　26.5-40　GHz.　Compute　Simulation　Technology-Microwave　Studio　(CST-MWS)　software　is　used　to　carry　out　simulation.　Results　indicate　that　the　phase　difference　of　the　reflection　coefficient　can　represent　the　thickness　of　TBC.　And　the　results　also　show　a　good　resolution　of　1o　change　in　phase　for　8　μm　TC　thickness　when　the　rectangular　waveguide　operates　at　relatively　high　frequency.　The　amplitude　of　the　reflection　coefficient　can　also　represent　the　thickness　of　TBC　when　the　rectangular　waveguide　operates　at　the　frequency　range　of　28.5-29.1　GHz.　The　results　are　consistent　with　simulation　result　obtained　using　CST-Microwave　Studio.