The　BJUT-II　VAD　(which　was　previously　called　the　intra-aorta　pump)　is　a　novel　left　ventricular　assist　device　(LVAD)　with　a　special　structure　and　connection　with　the　native　heart.　The　hemodynamic　effect　of　the　phase　difference　of　this　pump　on　the　cardiovascular　system　is　still　unclear.　In　this　work,　seven　speed　waveforms,　whose　phase　differences　vary　from　0　degrees　to　180　degrees,　are　used　to　evaluate　the　hemodynamic　effect　of　change　in　phase　difference　on　the　cardiovascular　system.　The　external　work　(EW),　equivalent　afterload　(EAL),　pulsatile　ratio　(PR),　and　mean　aortic　pressure　during　diastolic　period　(MAPD)　are　chosen　to　evaluate　the　hemodynamic　state　of　the　circulatory　system.　Mathematical　study　results　show　that　the　support　levels　generated　by　the　BJUT-II　VAD　under　various　phase　differences　are　comparable.　In　contrast,　EW,　EAL,　PR,　and　MAPD　are　significantly　affected　by　change　in　phase　difference.　It　is　found　that　EW　reaches　its　maximum　value　when　the　phase　difference　equals　30　degrees.　Similarly,　EAL　declines　with　increasing　phase　difference.　PR　reaches　its　maximum　value　when　the　phase　difference　is　at　60　degrees.　In　addition,　MAPD　decreases　with　increasing　phase　difference　and　then　achieves　its　maximum　value　at　30　degrees.　To　obtain　comprehensive　evaluation　of　the　hemodynamic　effects　of　phase　difference　on　the　cardiovascular　system,　a　weight　detection　algorithm　(WDA)　whose　output　indicates　the　hemodynamic　state　of　the　circulatory　system　is　also　designed,　with　EW,　PR,　and　MAPD　chosen　as　the　inputs.　The　minimum　value　of　the　output　of　the　WDA　indicates　the　optimal　hemodynamic　state　and　optimal　phase　difference　for　the　BJUT-II　VAD.　According　to　the　output　of　the　WDA,　30　degrees　is　considered　to　be　the　optimal　phase　difference　for　the　BJUT-II　VAD.