This　paper　proposes　a　new　multichannel　time　reversal　focusing　(MTRF)　method　for　circumferential　Lamb　waves　which　is　based　on　modified　time　reversal　algorithm　and　applies　this　method　for　detecting　different　kinds　of　defects　in　thick-walled　pipe　with　large-diameter.　The　principle　of　time　reversal　of　circumferential　Lamb　waves　in　pipe　is　presented　along　with　the　influence　from　multiple　guided　wave　modes　and　propagation　paths.　Experimental　study　is　carried　out　in　a　thick-walled　and　large-diameter　pipe　with　three　artificial　defects,　namely　two　axial　notches　on　its　inner　and　outer　surface　respectively,　and　a　corrosion-like　defect　on　its　outer　surface.　By　using　the　proposed　MTRF　method,　the　multichannel　signals　focus　at　the　defects,　leading　to　the　amplitude　improvement　of　the　defect　scattered　signal.　Besides,　another　energy　focus　arises　in　the　direct　signal　due　to　the　partial　compensation　of　dispersion　and　multimode　of　circumferential　Lamb　waves,　alongside　the　multichannel　focusing,　during　MTRF　process.　By　taking　the　direct　focus　as　a　time　base,　accurate　defect　localization　is　implemented.　Secondly,　a　new　phenomenon　is　exhibited　in　this　paper　that　defect　scattered　wave　packet　appears　just　before　the　right　boundary　of　truncation　window　after　time　reversal,　and　to　which　two　feasible　explanations　are　given.　Moreover,　this　phenomenon　can　be　used　as　the　theoretical　basis　in　the　determination　of　defect　scattered　waves　in　time　reversal　response　signal.　At　last,　in　order　to　detect　defects　without　prior　knowing　their　exact　position,　a　large-range　truncation　window　is　used　in　the　proposed　method.　As　a　result,　the　experimental　operation　of　MTRF　method　is　simplified　and　defect　detection　and　localization　are　well　accomplished.　(C)　2014　Elsevier　B.V.　All　rights　reserved.