Background:　In　coronary　artery　bypass　grafting　(CABG),　the　patency　of　venous　sequential　graft　remains　controversial.　Hemodynamic　factors　have　been　proved　to　be　the　important　factors　influencing　graft　patency.　The　objective　of　this　study　is　to　compare　the　patency　of　sequential　grafts　and　normal　grafts　by　hemodynamic　environment.　Methods:　This　study　used　a　patient＇s　clinical　data　to　construct　a　0D/3D　coupled　multi-scale　model,　and　used　this　model　to　calculate　graft＇s　hemodynamics　under　two　grafting　methods.　Meanwhile,　CABG　ideal　models　were　constructed　based　on　grafts＇　flow　data　of　60　patients　(63　normal　grafts,　19　sequential　grafts)　to　calculate　grafts＇　hemodynamics.　Results:　Based　on　the　multi-scale　model,　it　was　found　that　the　sequential　graft　flow　and　time　average　wall　shear　stress　(TAWSS)　were　higher　than　normal　graft,　which　was　good　for　graft　patency.　But　there　were　a　flow　separation　region,　some　regions　of　high　oscillatory　shear　index　(OSI)　and　relative　residence　time　(RRT)　in　sequential　graft,　which　could　lead　to　intimal　hyperplasia.　Based　on　ideal　CABG　models,　it　was　known　that　failure　rate　of　sequential　and　normal　grafts　were　36.8%　and　36.5%,　and　there　were　significant　differences　between　them　in　flow　rate,　TAWSS　and　OSI　(sequential　versus　normal:　flow　rate　(ml/min):　42.26　+/-　17.98　versus　27.33　+/-　14.52,　TAWSS　(Pa):　0.71　+/-　0.28　versus　0.54　+/-　0.25,　OSI:　0.0114　+/-　0.0029　versus　0.0047　+/-　0.0020).　Conclusion:　For　saphenous　venous　graft　(SVG),　although　the　normal　graft　has　similar　patency　with　the　sequential　graft,　the　hemodynamic　mechanism　behind　it　is　different.　In　flow　rate　and　WSS,　sequential　grafts　have　an　advantage　over　normal　grafts.　But　there　are　high　OSI　and　RRT　regions　in　sequential　grafts.