The glucoamylase produced by strain CL-6 was two-fold hastened when the organism was grown on media containing corncob. Strain CL-6 isolated from sweet starter was identified by morphological observation and ITS sequence analysis and indicated as Rhizopus oryzae. The enzymatic activity was measured by glucose oxidase-peroxide enzyme (GOD-POD). The sugar components in corncob were determined by thin-layer chromatography (TLC) and HPLC-RID. The sugars in the water-soluble components of the corncob were as follows: sucrose(520.33 mg/2.5 g wet resin), glucose (242.67 mg/2.5 g wet resin), fructose(228.67 mg/2.5 g wet resin) and maltose(30.33 mg/2.5 g wet resin). The effect of separately adding corncob, soluble fractions of corncob, sugar components and soluble fractions with molecular weight higher than 8~14.4 KD on the activity of glucoamylase were analyzed It was showed that glucoamylase formation was not enhanced when the organisms grew on media containing the four sugars, and the components with molecular weight exceeding 8~14.4 KD in the water-soluble parts of corncob was the important factor in stimulating glucoamylase prodution by Rhizopus oryzae CL-6.