Magnetic　hyperthermia　ablates　tumor　cells　by　absorbing　the　thermal　energy　from　magnetic　nanoparticles　(MNPs)　under　an　external　alternating　magnetic　field.　The　blood　vessels　(BVs)　within　tumor　region　can　generally　reduce　treatment　effectiveness　due　to　the　cooling　effect　of　blood　flow.　This　paper　aims　to　investigate　the　cooling　effect　of　BVs　on　the　temperature　field　of　malignant　tumor　regions　using　a　complex　geometric　model　and　numerical　simulation.　For　deriving　the　model,　the　Navier-Stokes　equation　for　blood　flow　is　combined　with　Pennes　bio-heat　transfer　equation　for　human　tissue.　The　effects　on　treatment　temperature　caused　by　two　different　BV　distributions　inside　a　mammary　tumor　are　analyzed　through　numerical　simulation　under　different　conditions　of　flow　rate　considering　a　Fe-Cr-Nb-B　alloy,　which　has　low　Curie　temperature　ranging　from　42 °C　to　45 °C.　Numerical　results　show　that　the　multi-vessel　system　has　more　obvious　cooling　effects　than　the　single　vessel　one　on　the　temperature　field　distribution　for　hyperthermia.　Besides,　simulation　results　show　that　the　temperature　field　within　tumor　area　can　also　be　influenced　by　the　velocity　and　diameter　of　BVs.　To　minimize　the　cooling　effect,　this　article　proposes　a　treatment　method　based　on　the　increase　of　the　thermal　energy　provided　to　MNPs　associated　with　the　adoption　of　low　Curie　temperature　particles　recently　reported　in　literature.　Results　demonstrate　that　this　approach　noticeably　improves　the　uniformity　of　the　temperature　field,　and　shortens　the　treatment　time　in　a　Fe-Cr-Nb-B　system,　thus　reducing　the　side　effects　to　the　patient.　©　2017　Elsevier　B.V.