Background:　Left　ventricular　assist　device　(LVAD)　has　been　widely　used　as　an　alternative　treatment　for　heart　failure,　however,　aortic　regurgitation　is　a　common　complication　in　patients　with　LVAD　support.　And　the　0-A　angle　(the　angle　between　LVAD　outflow　graft　and　the　aorta)　is　considered　as　a　vital　factor　associated　with　the　function　of　aortic　valve.　To　date,　the　biomechanical　effect　of　the　O-A　angle　on　the　aortic　valve　remains　largely　unknown.　The　aim　of　this　study　was　to　evaluate　the　0-A　angle　how　to　influence　the　aortic　valve　biomechanical　properties.　Methods:　The　current　study　employed　a　novel　fluid-structure　interaction　(FSI)　model　that　integrates　the　Lattice　Boltzmann　method　(LBM)　and　the　finite　element　method　(FEM)　to　investigate　the　biomechanical　effect　of　the　O-A　angle　on　the　aortic　valve　under　LVAD　support.　The　biomechanical　status　of　the　aortic　valve　was　evaluated　at　three　different　O-A　angles　(45,　90　and　135　degrees)　and.　four　indicators,　including　stress　distribution,　the　mean　stress,　the　axial　hemodynamic　force　(AHF)　and　the　wall　shear　stress　(WSS)　distribution　were　evaluated　at　three　timepoints　(28,　133,　and　266　ms).　Results:　The　results　showed　that　the　stress　and　the　high-stress　region　on　the　aortic　leaflets　increased　as　the　O-A　angle　increased　and　as　the　difference　between　the　left　ventricular　pressure　(LVP)　and　aortic　pressure　(AP)　increased.　And　the　aortic　insufficiency　was　observed　at　the　28　ms　(systolic　phase)　in　the　135-degree　0-A　angle.　During　the　systolic　phase,　significant　fluctuation　in　the　mean　stress　was　observed　when　the　0-A　angle　was　90　or　135　degrees.　During　the　diastolic　phase,　the　mean　stress　increased　in　the　three　O-A　angle　conditions　when　the　difference　between　the　LVP　and　AP　increased.　Regarding　to　the　AHF,　an　obvious　fluctuation　was　observed　during　the　systolic　phase　(0-100　ms)　in　the　135-degree　O-A　angle.　During　the　diastolic　phase,　the　AHF　increased　in　the　three　O-A　angle　conditions　when　the　difference　between　the　LVP　and　AP　increased.　For　the　WSS　distribution　evaluation,　the　WSS　was　increased　when　the　O-A　angle　increased.　At　28　ms　(the　systolic　phase),　a　high　WSS　was　located　on　the　free　edge　of　the　leaflets,　and　the　deformed　leaflets　were　observed　in　the　135-degree　0-A　angle.　And　at　133　ms　(the　rapid　diastolic　phase),　a　high　WSS　was　observed　at　the　free　edge　of　the　leaflets　when　the　0-A　angles　were　45　or　90　degrees,　and　at　both　free　edge　and　belly　of　the　leaflets　in　the　135-degree　0-A　angle.　Conclusions:　The　O-A　angle　is　closely　associated　with　the　biomechanical　status　of　the　aortic　valve　under　LVAD　support.　A　large　0-A　angle　caused　high　stress　and　WSS　on　the　aortic　leaflets,　as　well　as　broad　stress　and　WSS　distribution,　thus　leading　to　deformed　leaflets　and　retrograde　flow.　Therefore,　optimization　of　the　O-A　angle　will　favor　to　maintain　aortic　valve　function.