Air-coupled　ultrasonic　transducers　are　used　to　generate　and　receive　Lamb　waves　in　quasi-isotropic　laminated　composite　beams　for　delamination　detection.　The　influence　of　incident　angle　on　the　excited　mode　is　studied.　Numerical　calculation　and　experimental　results　show　that　a　pure　Lamb　wave　mode　can　be　generated　if　the　transmitting　transducer　is　oriented　at　a　specific　angle,　and　the　receiving　transducer　can　either　be　oriented　to　detect　the　same　mode　as　that　generated　by　the　transmitter　or　to　detect　another　mode　generated　by　mode　conversion　at　a　defect.　A　three-dimensional　finite　element　model　is　created　to　predict　the　interaction　of　Lamb　waves　with　delamination,　and　some　unique　mechanisms　of　interaction　between　A(0)　mode　Lamb　waves　and　delamination　are　revealed　in　detail.　The　experimental　results　obtained　on　laminated　composite　beam　using　air-coupled　ultrasonic　transducers　are　well　in　accordance　with　finite　element　simulation　results.　Research　results　show　that　air-coupled　ultrasonic　guided　waves　can　be　used　for　delamination　damage　detection　effectively　in　laminated　composite　beams.