Abstract: Based on the FMCW THz technology, the nondestructive testing technology of silica-alumina composite insulation tile for hypersonic vehicle and near space vehicle is studied. The THz spectrum characteristics of the tested material are analysed, and the simulated defect test block suitable for THz wave non-destructive testing is designed. The simulated defects of including cracks and holes are set up in different buried depths. The detection of crack and hole in the material is successfully realized by defect signal reflection method and bottom echo reflection method. The optimized detection process is given by experimental measurement. Finally, the detection process is verified by the real crack in the ceramic matrix composite insulation tile.