Background　and　objectives　A　quick　calculation　approach　of　steady-state　fractional　flow　reserve　(FFRss)　based　on　computed　tomography　angiography　(CTA)　images　is　a　reliable　non-invasive　way　of　calculate　FFR,　the　assumptions　used　in　the　research　should　be　study　further　to　increase　forecast　accuracy.　The　effect　of　inlet　and　outlet　boundary　conditions　on　FFRss　was　investigated.　Methods　15　patients　who　had　been　diagnosed　with　coronary　artery　disease　were　enrolled　in　this　study.　We　investigated　the　sensitivity　of　calculating　FFR　to　boundary　circumstances,　using　invasive　FFR　as　a　benchmark.　There　are　two　types　of　inlet:　(1)　aortic　pressure　based　on　clinically　measured.　(2)　mean　pressure　calculated　based　on　physiological　formula;　we　further　studied　the　outlet　changes　of　FFRss　under　different　coronary　vasodilation　responses　(24%,　48%,　72%).　Results　According　to　the　calculate　FFR　results　of　all　patients,　FFRSST　(based　on　the　clinical　experiment)　and　FFRSSM　(based　on　the　physiological　formula)　{r　=　0.99,　[95%　confidence　interval　(CI):0.0.94　to　1.14]　(p　＜　0.001)}.　Although　the　pressure　difference　between　the　two　pressure　boundary　conditions　is　15　mmHg,　the　calculated　FFR　result　does　not　change　significantly.　The　microcirculation　resistance　of　the　outlet　gradually　rose　as　the　vasodilation　state　changed,　and　the　computed　FFR　increased.　Conclusions　A　numerical　analysis　of　the　effects　of　proximal　and　distal　boundary　constraints　of　computational　models　on　computed　CT-FFR　is　presented.　The　findings　revealed　that　distal　boundary　circumstances　(hyperemic　vasodilation　response　of　coronary　micro-vessels)　have　a　significant　impact　on　FFR,　providing　evidence　to　guide　the　development　and　application　of　a　computational　model　for　estimating　FFR.