For　an　operating　wind　turbine,　the　main　shaft　suffers　severe　structural　damage.　The　surface　breaking　transverse　crack　threatens　the　safety　of　drive-train　system　directly.　The　crack　examination　method　is　available　by　diffracted　waves　in　the　central　hole.　In　this　research,　an　electromagnetic　acoustic　transducer　(EMAT)　for　receiving　diffracted　longitudinal　waves　is　proposed.　Firstly,　the　converse　piezomagnetic　stress　coefficients　and　magnetostriction　coefficient　were　derived　from　the　measured　magnetic　characteristic　curve.　The　measured　parameters　were　provided　for　sensor　simulation.　Considering　the　two　coupling　mechanisms,　a　receiving　EMAT　model　was　established　for　coil　optimization.　Secondly,　the　influence　of　materials,　lift-off　distance　and　cable　type　on　sensor　impedance　would　be　analyzed　in　detail.　Multiple　factors　were　taken　into　account　for　impedance　matching,　and　the　signal　amplitude　was　improved　significantly.　The　angle　divergence　of　the　EMAT　was　also　measured,　showing　the　main　lobe　with　24　degrees.　The　crack　detection　experiments　were　carried　out　on　a　shaft　sample.　The　results　show　that　the　developed　EMAT　can　achieve　the　reception　of　diffracted　longitudinal　waves,　and　the　signals　are　distinguishable.　The　crack　was　evaluated　simultaneously　by　the　received　diffracted　waves,　and　the　errors　showed　less　than　3　mm.