The　integrity　of　the　main　shaft　plays　a　significant　role　in　the　safety　of　wind　turbine.　Stress　concentration　often　occurs　where　the　main　shaft　and　the　bearing　are　assembled　in　the　wind　turbine.　The　surface　breaking　of　transverse　crack　on　the　outer　circumference　thus　becomes　a　major　dangerous　source.　In　this　research,　a　finite　element　(FE)　model　is　developed　to　analysis　the　echoes　on　the　end　face,　which　are　often　confused　in　the　identification　of　the　crack　signals.　The　propagation　of　ultrasonic　waves　and　its　reflection　on　the　shaft　boundary　will　be　investigated　in　details.　The　relationship　between　the　amplitude　of　the　crack　echo　and　the　radial　position　of　the　piezoelectric　transducer　is　explored　optimized　comprehensively.　Then,　an　ultrasonic　measurement　methodology　are　established　for　the　examination　of　the　main　shaft　from　the　end　face.　A　circular　scanning　experiment　for　the　shaft　testing　on　surface　cracks　have　been　implemented.　The　results　show　that　the　crack　depth　less　than　5　mm　can　be　examined,　although　the　total　size　of　the　shaft　is　phi　600　mm.　1285　mm.　All　artificial　cracks　in　the　high-stress　zone　have　been　detected　with　the　aid　of　a　B-scan　imaging,　which　reveals　the　position　of　defects.　This　research　will　provide　an　effective　regular　inspection　technique　for　the　wind　turbine　shaft　examination.