Terahertz　wave　propagation　in　marine　protective　coatings　and　its　non-destructive　testing　(NDT)　capability　were　studied　by　the　finite　difference　time　domain　(FDTD)　method.　The　FDTD　model　was　used　to　calculate　the　propagation　and　reflection　of　THz　radiation　from　marine　protective　coatings.　The　reflected　terahertz　waves　could　be　employed　in　coating　thickness　analysis　of　the　paint　layers.　In　order　to　clearly　identify　the　interface　between　antifouling　and　anticorrosive　coatings,　stationary　wavelet　transform　(SWT)　approach　was　applied　to　decompose　the　obtained　terahertz　impulse　functions　into　approximation　and　detail　coefficients;　SWT　detail　coefficients　were　used　for　the　feature　extraction　of　the　coating　thickness.　SWT　provides　a　more　accurate　identification　of　salient　features　in　a　signal,　such　as　the　weak　feature　between　antifouling　and　anticorrosive　coatings.　We　found　that　the　developed　model　and　SWT-based　algorithms　could　be　used　to　evaluate　the　occurrence　of　defects　beneath　the　coatings　(e.g.,　paint-off　and　corrosion　defects).　The　proposed　method　provides　the　solution　for　coating　thickness　of　marine　protective　coatings　and　it　would　benefit　the　effective　maintenance　to　avoid　coating　failure　and　facilitate　marine　protective　coating　design.　Therefore,　non-destructive　testing　and　evaluation　of　marine　protective　coating　system　by　terahertz　waves　with　SWT　could　be　recommended　for　engineering　applications.　©　2015　Elsevier　Ltd.　All　rights　reserved.