The　geometry　factors　have　prominent　impacts　on　the　flow　patterns　of　bypass　graft.　In　order　to　clarify　the　influence　of　graft　diameter　on　the　hemodynamics　of　femoral　bypass　graft,　the　pulsatile　blood　flows　in　three　bypassing　models　with　different　graft　diameters　were　Simulated　with　finite-element　method.　The　temporal-spatial　distributions　of　flow　patterns,　pressure　drops,　and　wall　shear　stresses　were　depicted　and　compared.　The　results　indicated　that　femoral　artery　bypassed　with　a　large　graft　demonstrates　relatively　better　and　more　profitable　hemodynamic　phenomena　with　large　longitudinal　velocity,　uniform　wall　shear　stress,　and　small　wall　shear　stress　gradient.　The　large　model　may　be　effective　in　decreasing　the　probability　of　the　initiation　and　development　of　postoperative　intimal　hyperplasia　and　restenosis.　Copyright　(C)　2007　John　Wiley　&　Sons,　Ltd.