Feature　extraction　of　marine　protective　coatings　using　Hilbert　transform　(HT)　and　wavelet　transform　modulus　maximum　(WTMM)　on　terahertz　pulsed　imaging　(TPI)　of　the　coatings　was　proposed.　For　TPI-based　marine　protective　coating　detection,　it　is　difficult　to　locate　exactly　the　reflected　echoes　form　internal　structure　of　coating　system　by　the　faint　feature　in　the　time　domain　due　to　the　interference　of　background　noise.　However,　those　faint　features　were　usually　caused　by　the　interface　between　two　different　medium　layers　whose　refractive　indices　are　very　similar　or　caused　by　micro　defects　beneath　the　coating.　The　proposed　algorithm　was　validated　by　simulated　and　experimental　TPI　waveform　obtained　from　marine　paint　samples　with　or　without　defects.　To　extract　the　structure　feature　more　clearly　and　intuitively,　Hilbert　transform　procedure　was　carried　out　on　detected　terahertz　signal　to　get　Hilbert　envelope　for　further　processing.　Subsequently,　the　modulus　maximum　of　the　stationary　wavelet　transform　approximation　coefficients　were　employed　as　the　criteria　for　feature　extraction　of　internal　interfaces　and　defect　features,　according　to　the　relationship　between　WTMM　and　signal　singularity.　The　results　demonstrated　that　the　combination　of　HT　and　WTMM　algorithms　could　be　used　to　exactly　extract　the　structure　feature　and　to　evaluate　the　position　of　defects　beneath　coatings.　©　2018