Becauseofthecharacteristicsofthehighvaporpressureofdomesticaviationfuel,afueltankcatalyticinerting systemwithanexternalairsupplyisproposed.Basedonthesuctiongasflow atthefueltankoutlet,theflowrelationship ofeachcomponentgas attheinletandoutletofeachpartofthesystemisderived.Basedonthemassconservationequa-tionandtheequilibriumdissolutionrelationshipofgas,themathematicalmodelofgasconcentration changeonfueltank ullageisestablished.Thecriticalcatalyticefficiencywasdeduced,andexperimentsverifiedthecorrectnessofthecorefu-eltankmodel.RP-3jetfuelistakenastheresearchobject.Theupperandlowerlimitsofthesupplementalgasratioarein-troduced,andtheeffectsofcatalytic efficiencyandsupplementarygasratio oncatalytic inertingsystemperformance are alsoanalyzed.Theresultsshowthatthesystemairsupplement canshortentheinertingtimewhenthecatalyticefficiency is higher than the critical value. Still, at the same time, the preheating power and the cooling gas flow need to be in-creased. In addition, when the catalytic efficiency is constant, there is an optimal solution for the air supplement ratio, whichispositivelyrelatedtothecatalyticefficiency.Theempiricalformulafortheoptimalsolutionissummarized.Since theinertingefficiencyis moreimportant,whendesigningthecatalytic inertingsysteminChinainthefuture,theinerting speedcanbeacceleratedbyaddinganairsupplementsystem.