This study were investigated the effects of physiologically active compounds isolated from Platycodon grandiflorum on streptozotocin-induced diabetic rats. The experimental groups were divided into six groups, normal, diabetic control (CM), and four experimental groups (inulin (IN), inulin + saponin (IS), oligosaccharide (OS), and total extract group (WE)). The rats have free access to water and diet. Experimental groups were administered orally with inulin (630 mg/mL), inulin (630 mg/mL) + saponin (25.2 mg/mL), oligosaccharide (367.5 mg/mL), and total extract (225 mg/mL) into the diabetic rats for 5 weeks after STZ injection; The levels of fasting blood glucose in diabetic control increased by 10.0% for 5 weeks, but the level of blood glucose in inulin and total extract groups decreased by 21.3% and 21.2%, respectively. The concentrations of total cholesterol and triglyceride in serum of diabetic rats fed physiologically activity compounds were lower than those in diabetic control rats. HDL-cholesterol was similar among all the groups. Weights of testicle and heart were lighter, while weight of kidney was significantly increased in diabetic groups than normal group. The concentrations of serum protein insulin and albumin in diabetic groups were significantly decreased compared with those of the normal group. Urinary glucose excretion was decreased in inulin group than other diabetic groups.