The　time-of-flight　diffraction　(TOFD)　technique　is　a　new　ultrasonic　nondestructive　testing　method.　It　utilize　the　longitudinal　diffraction　signal　that　generated　from　the　defects,　we　can　confirm　whether　there　is　a　discontinuity　in　butt　weld　by　the　analysis　of　diffracted　waves.　This　detection　method　has　wide　application　prospects　and　detect　flaws　with　high　precision　of　localization　and　quantification.　In　this　paper,　two-dimensional　numerical　simulation　of　ultrasonic　TOFD　technique　is　carried　out　on　unequal　thickness　butt　weld　of　Drum　Cylinder　and　Spherical　Head,　the　propagation　characteristics　and　laws　of　ultrasonic　wave　in　unequal　thickness　component　are　analyzed　by　using　finite　element　software　ABAQUS.　The　simulation　results　show　that　the　ABAQUS　software　can　effectively　simulate　ultrasonic　TOFD　technique　in　such　pressure　vessel　component,　so　the　application　range　of　ultrasonic　TOFD　technique　will　be　extended.　©　(2014)　Trans　Tech　Publications,　Switzerland.