In　order　to　detect　thermal　barrier　coating(TBC)　using　microwave　non-destructive　detection　technique　in　the　low　frequency,　the　detection　sensitivity,　optimization　of　detection　parameters　is　carried　out　detecting　thickness　and　porosity　of　thermal　barrier　coating,　and　detecting　crack　of　metal　substrate,　using　coaxial　probe　which　frequency　is　0-17　GHz.　The　influence　of　the　coaxial　probe　size,　standoff　distance,　thickness　and　porosity　of　top　coating(TC)　is　suited　using　CST-microwave　studio.　The　results　of　detecting　TC　thickness　show　that　the　smaller　the　probe　or　the　smaller　the　TC　dielectric　constant,　the　higher　the　frequency　when　phase　difference　equal　to　zero,　and　the　smaller　the　standoff　distance,　the　higher　the　detection　sensitivity.　The　results　of　detecting　TC　porosity　show　that　the　higher　the　detection　sensitivity,　the　larger　the　TC　thickness.　The　results　of　detecting　crack　of　metal　substrate　show　that　in　order　to　prevent　un-detection,　the　scanning　length　should　be　less　than　the　radius　of　the　probe.　Therefore,　it　is　feasible　to　detect　TBC　using　microwave　in　low　frequency,　when　coaxial　was　used　a　sensor.　©　2014　Journal　of　Mechanical　Engineering.