The　welding　defects　led　to　many　accidents　in　special　pressure　equipment.　The　welding　quality　directly　affected　the　product　safety　and　reliability.　Lamb　wave　technique　offered　rapid　scanning　ability　for　defect　detection　and　was　capable　of　evaluating　the　welding　quality　effectively.　A　3-dimensional　finite　element　model　was　developed　to　reveal　the　Lamb　wave　propagation　characteristics　in　butt　welds.　The　Lamb　wave　was　excited　at　the　weld　end　in　the　in-plane　direction.　The　simulation　results　indicated　the　existence　of　energy　trapping　and　energy　attenuation　phenomena　in　butt　welds.　The　variation　of　lamb　wave　propagation　characteristics　versus　the　weld　remaining-height,　weld　width　and　Young　modulus　were　investigated.　Experimental　results　verified　the　conclusions　obtained　from　finite　element　analysis　method.　The　results　could　provide　a　reference　method　for　the　butt　weld　quality　evaluation.