In　coronary　artery　bypass　grafting　(CABG),　graft＇s　poor　instant　patency　may　lead　to　an　abnormal　hemodynamic　environment　in　anastomosis,　which　could　further　cause　graft　failure　after　the　surgery.　This　paper　investigates　the　graft　hemodynamics　with　different　instant　patency,　and　explores　its　effect　on　graft　postoperative　efficiency.　Six　CABG　0D/3D　coupling　multi-scale　models　which　used　left　internal　mammary　artery　(LIMA)　and　saphenous　vein　(SVG)　as　grafts　were　constructed.　Different　types　of　grafts　were　examined　in　the　models,　including　normal　grafts,　grafts　with　competitive　flow　and　grafts　with　anastomotic　stenosis.　Simulation　results　indicated　that　comparing　with　SVG　grafts,　there　was　a　greater　difference　between　normal　LIMA　graft　and　non-patent　LIMA　graft.　Also,　the　backflow　occurred　even　in　LIMA　systolic　flow.　The　wall　shear　stress　(WSS)　in　the　graft　of　the　competitive　flow　LIMA　model　had　an　appreciable　decrease　comparing　with　the　normal　graft.　In　addition,　the　WSS　in　the　stenosis　region　of　the　anastomotic　stenosis　LIMA　model　was　much　higher　than　its　adjacent　regions.　In　contrast,　the　WSS　distributions　in　the　SVG　models　were　much　smoother　than　in　the　LIMA　models.　For　oscillatory　shear　index　(OSI),　there　was　little　difference　between　normal　LIMA　and　SVG.　But　when　the　graft　had　competitive　flow　or　anastomotic　stenosis,　much　higher　OSI　occurred　in　some　regions　in　LIMA　than　SVG.　There　are　significant　differences　in　hemodynamics　between　normal　grafts　and　non-patent　grafts　both　in　LIMA　and　SVG.　The　hemodynamic　environment　in　a　normal　LIMA　is　better　than　that　in　a　normal　SVG.　However,　in　the　situation　of　the　two　types　of　non-patent　grafts,　the　hemodynamics　of　SVG　is　better　than　LIMA.