Ceramic　matrix　composites　(CMC)　have　a　series　of　advantages　such　as　low　density　and　high　temperature　resistance,　and　are　widely　used　in　components　such　as　the　leading　edge　of　aircraft　wings　and　advanced　gas　turbine　engines.　Due　to　factors　such　as　diversified　manufacturing　processes　and　complicated　manufacturing　steps　in　the　production　process,　defects　inevitably　remain　in　the　material,　which　has　a　non-negligible　impact　on　the　stability　and　reliability　of　the　material.　In　response　to　the　urgent　need　for　internal　defect　detection,　based　on　the　advantages　of　rich　information　and　high　time　resolution　of　terahertz　time-domain　spectroscopy　(THz-TDS)　technology,　a　terahertz　detection　method　for　non-destructive　detection　of　internal　defects　of　CMC　is　proposed.　First,　the　reflective　THz-TDS　system　is　used　to　perform　non-contact　non-destructive　testing　on　the　prefabricated　CMC　sample,　and　point-by-point　scanning　detection　signals　are　obtained　in　the　sample.　Then,　in　view　of　the　obvious　phase　delay　phenomenon　that　often　occurs　in　the　high-frequency　signal　after　high-order　filtering,　a　zero-phase　filtering　method　is　proposed,　which　eliminates　the　phase　delay　and　accurately　extracts　information　such　as　peak　value,　phase　and　time-of-flight.　On　this　basis,　the　multi-feature　weighted　fusion　imaging　method　is　used　to　draw　the　two-dimensional　surface　imaging　results　of　the　material　defect,　and　the　corresponding　three-dimensional　defect　topography　is　reconstructed,　and　the　defect　topography　position　information　is　visually　displayed,　and　the　location　and　quantitative　evaluation　of　the　defects　in　the　CMC　sample　are　achieved.　©　2023　Editorial　Office　of　Chinese　Journal　of　Mechanical　Engineering.　All　rights　reserved.