Crack　is　one　of　the　main　reasons　for　structure　failure,　and　using　ultrasonic　Lamb　wave　can　efficiently　locate　it　in　plate-like　structures.　Currently　this　technology　can＇t　achieve　specific　characteristics　of　defects.　Research　on　the　interaction　of　Lamb　waves　with　defects　provides　principle　bases　for　high　resolution　inspection.　Scattering　parameter　matrix(S-matrix)　is　employed　to　present　the　interaction　of　elastic　wave　with　defects.　FE　and　experiment　research　on　Lamb　wave　oblique　incident　to　crack　is　studied.　Results　illustrated　that　scattering　field　is　non-uniform　and　show　significant　beam　form　phenomenon.　With　incident　angle　changing　from　0°　to　90°,　the　angle　of　the　beam　non-monotonic　changes　and　energy　of　scattering　wave　rapidly　decreases.　When　incident　angle　equal　0°　and　90°,　S-matrix　is　symmetric　so　that　can　be　used　to　evaluate　the　expanding　direction　of　crack.　Using　the　characteristic　of　Lamb　wave　scattering　in　crack　with　oblique　incident,　more　reasonable　imaging　algorithms　and　transducer　distribution　methods　can　be　designed,　which　will　provide　an　efficient　way　to　inspect　the　crack　with　high　resolution.　©　2013　Journal　of　Mechanical　Engineering.