Fractional　flow　reserve　(FFR)　is　the　gold　standard　to　identify　individual　stenosis　causing　myocardial　ischemia　in　catheter　laboratory.　The　purpose　of　this　study　is　to　present　a　fast　simulation　method　to　estimate　FFR　value　of　a　coronary　artery,　which　can　evaluate　the　performance　of　vascular　stenosis,　based　on　resistance　boundary　conditions.　A　patient-specific　3-dimensional　(3D)　model　of　the　left　coronary　system　with　intermediate　diameter　stenosis　was　reconstructed　based　on　the　CTA　images.　The　resistance　boundary　conditions　used　to　simulate　the　coronary　microcirculation　were　computed　based　on　anatomical　reconstruction　of　coronary　3D　model.　This　study　was　performed　by　coupling　the　3D　coronary　tree　model　with　the　lumped　parameter　model　(OD　model).　The　flow　rate　and　pressure　of　coronary　tree　were　calculated　in　twenty　minutes.　In　addition,　the　effect　of　inlet　pressure　and　myocardial　mass　on　FFRss　values　has　been　investigated.　The　results　showed　that　the　effect　of　myocardial　mass　was　greater　than　the　effect　of　inlet　pressure　on　FFRss.　This　FFRss　simulation　method　can　quickly　and　accurately　assess　the　influence　of　coronary　stenosis　in　aid　clinical　diagnosis.