Background:　The　underuse　of　invasive　fraction　flow　reserve　(FFR)　in　clinical　practice　has　motivated　research　towards　its　non-invasive　prediction.　The　early　attempts　relied　on　solving　the　incompressible　three-dimensional　Navier-Stokes　equations　in　segmented　coronary　arteries.　However,　transient　boundary　condition　has　a　high　resource　intensity　in　terms　of　computational　time.　Herein,　a　method　for　calculating　FFR　based　on　steady-state　geometric　multiscale　(FFRSS)　is　proposed.Methods:　A　total　of　154　moderately　stenotic　vessels　(40-80%　diameter　stenosis)　from　136　patients　with　stable　angina　were　included　in　this　study　to　validate　the　clinical　diagnostic　performance　of　FFRSS.　The　method　was　based　on　the　coronary　artery　model　segmented　from　the　patient＇s　coronary　CTA　image.　The　average　pressure　was　used　as　the　boundary　condition　for　the　inlet,　and　the　microcirculation　resistance　calculated　by　the　coronary　flow　was　used　as　the　boundary　condition　for　the　outlet　to　calculate　the　patient-specific　coronary　hyperemia.　Then,　the　flow　velocity　and　pressure　distribution　and　the　FFRss　of　each　coronary　artery　branch　were　calculated　to　evaluate　the　degree　of　myocardial　ischemia　caused　by　coronary　stenosis.　Also,　the　FFRSS　and　FFRCT　of　all　patients　were　calculated,　and　the　clinically　measured　FFR　was　used　as　the　＂gold　standard＂　to　verify　the　diagnostic　performance　of　FFRSS　and　to　compare　the　correlation　between　FFRSS　and　FFRCT.Results:　According　to　the　FFRSS　calculation　results　of　all　patients,　FFRSS　and　FFR　have　a　good　correlation　(r　=　0.68,　p　＜　0.001).　Similarly,　the　correlation　of　FFRSS　and　FFRCT　demonstrated　an　r　of　0.75　(95%CI:　0.67-0.72)　(p　＜　0.001).　On　receiver-operating　characteristic　analysis,　the　optimal　FFRSS　cut　point　for　FFR　＜=　0.80　was　0.80　(AUC:0.85　[95%　confidence　interval:　0.79　to　0.90];　overall　accuracy:88.3%).　The　overall　sensitivity,　specificity,　PPV,　and　NPV　for　FFRSS　＜=　0.80　versus　FFR　＜=　0.80　was　68.18%　(95%　CI:　52.4-81.4),　93.64%　(95%　CI:　87.3-97.4),　82.9%,　and　91.1%,　respectively.Conclusion:　FFRSS　is　a　reliable　diagnostic　index　for　myocardial　ischemia.　This　method　was　similar　to　the　closed-loop　geometric　multiscale　calculation　of　FFR　accuracy　but　improved　the　calculation　efficiency.　It　also　improved　the　clinical　applicability　of　the　non-invasive　computational　FFR　model,　helped　the　clinicians　diagnose　myocardial　ischemia,　and　guided　percutaneous　coronary　intervention.