This study undertook exploration of Indonesian Dahliaplant (Dahlia variabilis), that can potentially be developed as the source of inulin. Aspergillus clavatus Gmn11.3 was an endophytic fungi isolated from Brastagi’s Dahlia rizhosphere which had been previously reported to show high inulinase activity by producing wide halo zone around the colonies. This research aimed to optimize the production of inulinase by A.clavatus Gmn11.3.Inulinase production was carried out using the best inducer;1% inulin in a medium containing 0.05% MgSO4.7H2O; 0.015% FeSO4; 0.2% NaCl, 0.05%KCl, and 1.0% yeast extract at 370C, pH 4.5, and 5 days incubation (120 hours).The crude extract of extracellular enzyme was purified by ammonium sulphate precipitation, followed by Sephadex G75 and G50 gel filtration, DEAE cellulose and DEAE-Toyopearl anion exchanger-column chromatography. The purity of extracellular enzyme was monitored using SDS PAGE. Inulinase purity increased 5.91 fold after ammonium sulphate-fractionation, and 71.66 fold after purification using gel filtration-column chromatography and ion exchange-column chromatography. Inulinase from A. clavatus Gmn11.3 showed higher affinity than to its substrates with Km 0.078mM and 0.039mM, and Vmax were 0.098mM/h and 0.041mM/h respectively at optimum pH 5.0; temperature 500C at four hours-incubation time; and its molecular weight were estimated to be 65.2KDa and 62.4KDa. Whilstinulinase from A. niger Gmn11.1, as a comparison, had a Km and Vmax value 0.021mM and 0.022mM/h respectively at optimum pH 4.6; temperature 450C with 15 hours incubation time; and its molecular weight was estimated to be 63KDa.