Numerical　simulation　of　longitudinal　crack　detection　in　pipe　using　ultrasonic　guided　wave　T(0,1)　mode　was　made.　A　valid　finite　element　model　with　longitudinally　oriented　through-thickness　crack　of　various　length　was　given,　on　which　T(0,1)　mode　ultrasonic　guided　wave　was　excited.　The　results　of　numerical　simulation　showed　the　relation　between　longitudinal　length　and　reflection　coefficient　which　was　defined　as　the　amplitude　of　the　reflected　signal　divided　by　the　amplitude　of　the　incident　signal　as　well　as　the　circumferential　distribution　of　reflected　signal　amplitude.　Method　to　determine　location　of　longitudinal　and　circumferentially　locating　crack　using　T(0,　1)　mode　ultrasonic　guided　wave　was　also　introduced.　Simulation　results　show　that　T(0,1)　mode　is　sensitive　to　longitudinal　crack　detection　and　the　circumferential　position　where　maximal　reflection　is　received　is　the　same　with　the　circumferential　position　of　longitudinal　crack,　as　a　whole,　the　reflection　coefficient　shows　an　increasing-decreasing　tendency.