Hemodynamic　factors　may　affect　the　potential　occurrence　of　in-stent　restenosis　(ISR)　after　intervention　procedure　of　vertebral　artery　ostial　stenosis　(VAOS).　The　purpose　of　the　present　study　is　to　investigate　the　influence　of　stent　protrusion　length　in　implantation　strategy　on　the　local　hemodynamics　of　the　VAOS.　CTA　images　of　a　58-year-old　female　patient　with　posterior　circulation　transient　ischemic　attack　were　used　to　perform　a　3D　reconstruction　of　the　vertebral　artery.　Five　models　of　the　vertebral　artery　before　and　after　the　stent　implantation　were　established.　Model　1　was　without　stent　implantation,　Model　2-5　was　with　stent　protruding　into　the　subclavian　artery　for　0,　1,　2,　3mm,　respectively.　Computational　fluid　dynamics　simulations　based　on　finite　element　analysis　were　employed　to　mimic　the　blood　flow　in　arteries　and　to　assess　hemodynamic　conditions,　particularly　the　blood　flow　velocity　and　wall　shear　stress　(WSS).　The　WSS　and　the　blood　flow　velocity　at　the　vertebral　artery　ostium　were　reduced　by　85.33　and　35.36%　respectively　after　stents　implantation.　The　phenomenon　of　helical　flow　disappeared.　Hemodynamics　comparison　showed　that　stent　struts　that　protruded　1mm　into　the　subclavian　artery　induced　the　least　decrease　in　blood　speed　and　WSS.　The　results　suggest　that　stent　implantation　can　improve　the　hemodynamics　of　VAOS,　while　stent　struts　that　had　protruded　1mm　into　the　subclavian　artery　would　result　in　less　thrombogenesis　and　neointimal　hyperplasia　and　most　likely　decrease　the　risk　of　ISR.