Intracranial　aneurysms　can　be　classified　into　thick-walled　aneurysms　and　thin-walled　aneurysms　according　to　their　intraoperative　appearances;　previous　publications　have　revealed　that　different　kinds　of　intraoperative　appearances　were　associated　with　intraoperative　rupture　and　postoperative　complications.　Here,　we　tried　to　evaluate　the　association　between　hemodynamic　features　and　aneurysm　wall　appearance　using　computational　fluid　dynamics　(CFD)　method.　Forty-one　consecutive　patients　with　unruptured　middle　cerebral　artery　(MCA)　bifurcation　aneurysms　were　included　in　our　study.　Based　on　the　appearances　observed　under　the　microscope,　aneurysms　were　classified　into　two　different　types:　thick-walled　and　thin-walled　aneurysms.　Preoperative　computed　tomographic　angiography　(CTA)　was　used　for　geometry　reconstruction　and　CFD　analysis.　Morphological　and　hemodynamic　parameters　were　compared　between　the　two　groups.　Eighteen　aneurysms　were　classified　as　thick-walled　atherosclerotic　ones　according　to　their　intraoperative　appearances.　Compared　with　thin-walled　aneurysms,　aneurysms　with　atherosclerotic　changes　had　larger　geometry　parameters　(aneurysm　depth,　maximum　height,　diameter,　aspect　ratio,　size　ratio),　lower　wall　shear　stress　(WSS),　and　larger　low　WSS　area　ratio　(LSAR).　Thick-walled　aneurysms　characterized　by　atherosclerotic　changes　are　associated　with　low　WSS　and　larger　LSAR.　CFD　may　be　a　useful　tool　for　discriminating　the　intraoperative　appearance　of　cerebral　aneurysms.