In　order　to　assess　the　variability　in　the　calculation　of　the　pressure　gradient　through　a　moderate　thoracic　aortic　coarctation　(MTAC),　a　3D　finite　element　model　of　MTAC　was　constructed,　which　includes　the　ascending　aorta,　the　aortic　arch,　the　descending　aorta,　and　the　three　large　branches　(the　innominate　artery,　the　left　common　carotid　artery,　and　the　left　subclavian　artery),　as　well　as　with　a　coarctation　in　the　descending　aorta.　The　surface　model　of　MTAC　in　STL　format　was　imported　into　ANSYS　ICEM　CFD12.1　to　generate　volume　mesh.A　finite　element　model　suitable　for　hemodynamics　analysis　of　patient-specific　MTAC　was　established.Numerical　simulation　of　hemodynamics　in　this　model　was　performed　by　means　of　Computational　fluid　dynamics　(CFD)　using　ANSYS　CFX12.1.　The　temporal　distributions　of　homodynamic　variables　such　as　streamlines,　wall　pressure,　velocity　vector　and　wall　shear　stress　in　the　arteries　were　analyzed　during　a　cardiac　cycle.　The　maximum　and　the　average　of　pressure　gradient　in　a　cardiac　cycle　through　a　MTAC　are　13　mmHg　and　2.84　mmHg　respectively.　The　pressure　difference　between　the　systolic　and　the　diastolic　in　a　cardiac　cycle　proximal　to　the　coarctation　is　about　38　mmHg,　which　is　smaller　than　the　difference　between　the　recorded　systolic　and　diastolic　pressures　of　115　and　65　mmHg　(i.e.　the　difference　is　115-65=50).　Similarly,　the　pressure　gradient　through　the　coarctation　under　exercise　conditions　could　be　predicted　via　modifying　the　inflow　and　outflow　boundary　conditions　under　resting　conditions.　CFD　techniques　make　it　possible　to　obtain　information　(such　as　pressure　when　the　patient　is　under　exercise　condition)　which　is　difficult　to　get　in　clinic　practice　or　in　experiment　based　on　patient-specific　data.　©　2013　Springer-Verlag.