The　objective　study　was　to　estimate　the　rheological　properties　and　physiological　compatibility　of　the　blood　pump　by　simulating　the　internal　flow　field　of　the　blood　pump.　In　this　study　we　use　computational　fluid　dynamics　method　to　simulate　and　analyse　two　models　of　axial　blood　pumps　with　a　three-blade　diffuser　and　a　six-blade　diffuser,　named　pump　I　and　pump　II,　respectively,　and　to　compare　the　flow　patterns　of　these　two　kinds　of　blood　pumps　while　both　of　them　satisfy　the　conditions　of　the　normal　human　blood　differential　pressure　and　blood　flow.　Results　indicate　that　(i)　the　high　shear　force　occurs　between　the　diffuser　and　the　rotor　in　which　the　crucial　place　leads　to　haemolysis　and　(ii)　under　the　condition　of　100mmHg　pressure　head　and　5l/min　flow　rate,　the　difference　between　the　two　kinds　of　blood　pumps,　as　far　as　the　haemolytic　performance　is　concerned,　is　notable.　The　haemolysis　index　of　the　two　pumps　is　0.32%　and　0.2%.　In　conclusion,　the　performance　of　the　blood　pump　is　influenced　by　the　diffusers＇　blade　number.　Pump　II　performed　better　than　pump　I,　which　can　be　the　basic　model　for　blood　pump　option.