Switch　rail　defect　is　one　of　the　important　safety　hazards　in　turnout　system.　The　flat-plate　magnetostrictive　sensor　was　used　to　excite　30,　70　and　100　kHz　horizontal　shear　waves　at　the　bottom　of　the　rail　to　monitor　the　head　and　bottom　defects　of　the　pointed　rail　in　this　paper.　First,　the　influence　of　ambient　temperature　on　wave　packet　energy　of　the　reflected　echo　of　the　characteristic　structure　in　the　switch　rail　was　studied.　The　wave　packet　energy　was　observed　increases　approximately　linearly　with　temperature.　The　method　of　energy　ratio　between　characteristic　signal　and　reference　signal　was　proposed　to　effectively　compensate　the　influence　of　temperature　on　monitoring　results.　Second,　the　guided　wave　monitoring　experiment　was　carried　out　in　the　process　of　increasing　the　volume　of　the　rail　head　and　rail　bottom　defects.　The　characteristics　of　the　defects　and　the　reflected　wave　packet　energy　at　the　rear　end　were　“first　raised　and　then　suppressed”,　which　enhanced　the　recognition　ability　of　guided　waves　to　the　defects.　Taking　30　kHz　and　70　kHz　guided　waves　as　examples,　they　could　identify　the　rail　bottom　defects　of　20.　0　mm　in　length,　2.　0　mm　in　width　and　7.　1　mm　in　depth,　and　the　rail　head　defects　of　38.　6　mm　in　length,　2.　0　mm　in　width　and　10.　1　mm　in　depth,　respectively.　Results　show　that　the　magnetostrictive　guided　wave　technology　can　realize　the　effective　monitoring　of　switch　rail　defects,　and　has　important　engineering　application　prospects.　©　2023　Beijing　University　of　Technology.　All　rights　reserved.