In　previous　published　research,　the　deployment　of　flow-diversion　increases　the　intra-aneurysmal　pressure　by　20　mmHg　in　the　case　with　a　pre-aneurysm　stenosis.　The　purpose　of　this　study　is　to　learn　the　influence　to　the　aneurysm　when　a　pre-aneurysm　stenosis　exists　which　may　threaten　people＇s　health　even　more　severely.　In　the　present　research,　idealized　models　of　straight　and　curved　blood　vessels　with　both　aneurysm　and　pre-aneurysm　stenosis　were　established,　with　altering　the　degree　of　stenosis,　the　distance　between　stenosis　and　aneurysm　and　the　curvature　of　parent　artery.　As　the　degree　of　stenosis　increases,　the　reattachment　length　increases　in　straight　vessels.　Different　positions　of　reattachment　points　to　aneurysm　neck　affect　the　flow　pattern　inside　the　aneurysm.　In　the　model　with　higher　degree　of　stenosis　and　smaller　distance　between　stenosis　and　aneurysm,　the　flow　pattern　and　the　direction　of　vortexes　inside　the　aneurysm　are　affected　by　the　recirculation　after　stenosis.　Driven　by　inertial　force,　reattachment　length　decreases　as　the　curvature　of　the　parent　artery　increases,　and　stream　inside　the　aneurysm　is　affected　only　when　the　distance　between　stenosis　and　aneurysm　is　short　enough.　In　all　models,　the　pressure　drop　inside　the　aneurysm　increases　as　the　degree　of　stenosis　increases,　creating　a　lower　pressure　environment　in　the　aneurysm.　©　2014　The　Japan　Society　of　Mechanical　Engineers.