As　a　promising　nondestructive　testing　(NDT)　technique　with　a　very　adaptive　physical　modeling　of　wave　transmission　process,　terahertz　technology　is　used　for　the　detection　and　characterization　of　nonpolar　materials　and　the　evaluation　of　layered　and/or　defective　structures.　THz-TDS　can　also　be　used　to　perform　spectroscopic　analysis　and　detect　structural　defects　in　thermal　barrier　coatings　(TBCs)　of　aero-engines.　Although　it　is　generally　difficult　to　measure　the　structure　of　the　thin　oxide　layer　of　the　thermal　barrier　coatings　whose　thickness　is　generally　lower　than　30　g　m　(the　current　axial　resolution　of　the　THz-TDS　cannot　exceed　30　g　m).　We　were　able　to　complete　the　detection　of　the　oxide　layer　within　1-29　g　m　through　simulation　by　using　the　SWT-BP　algorithm.　In　this　study,　the　analysis　was　performed　on　real　-world　samples,　the　fitting　degree　of　the　SWT-BP　algorithm　reached　0.77,　and　the　minimum　prediction　error　was　less　than　0.1　g　m.　The　paper　also　put　forward　some　improvement　measures　about　the　experimental　results.　(c)　2024　Optica　Publishing　Group