An　intracranial　aneurysm　(IA)　is　a　pathological　dilatation　of　the　cerebral　artery　wall.　Blood　flow　and　pressure　inside　IA　are　not　steady.　Interaction　between　blood　flow　and　vessel　wall　reveals　stress　and　deformation　of　vessel　wall　in　vivo.　It　also　provides　more　true　and　reliable　information　about　blood　flow.　So　analysis　of　Fluid　Structure　Interaction　(FSI)　is　favor　of　proper　explanation　for　formation　and　development　of　aneuris-mal　disease.　Patient-specific　model　whose　parent　artery　has　a　large　＇S＇　bending　and　a　side　wall　aneurysm　was　constructed　from　CT　data.　Pulsatile　calculation　of　FSI　for　this　constructed　model　was　carried　out.　From　streamlines　it　can　be　found　that　there　is　an　obvious　vortex　flow　in　aneurismal　cavity　in　a　cardiac　cycle.　The　type　of　this　vortex　flow　is　not　changed　in　a　cardiac　cycle.　As　far　as　Wall　Shear　Stress　(WSS),　there　is　a　region　in　aneurismal　neck　where　the　value　of　WSS　is　relatively　high.　At　0.27s　in　a　cardiac　cycle,　deformation　of　the　vessel　wall　is　the　biggest.　There　are　two　regions　in　aneurismal　dome　where　the　value　of　Von　Mises　Stress　is　the　locally　biggest.　©　2011　IEEE.