In order to investigate the hypoglycemic effect of Ophiopogonis japonicas oligosaccharide on type 2 diabetes mellitus，the db/db diabetic mice were intragastrically administered with Ophiopogonis japonicas oligosaccharide for 8 weeks．The body weight and general physical signs were observed during the treatment．The fasting blood glucose levels were determined after 4 and 8 weeks of administration．The changes in 24 h urinary albumin excretion and 24 h urine protein amounts, glycosylated serum protein(GSP), total cholesterol(TC), triglyceride(TG), high density lipoprotein cholesterol(HDL-C) and low density lipoprotein cholesterol(LDL-C), urea nitrogen and creatinine levels in serum were measured after 8 weeks of treatment．Results showed that Ophiopogonis japonicas oligosaccharide could significantly lower the body weights, blood glucose levels and the AUCs during oral glucose tolerance test, and inhibited the changes of 24 h urinary albumin excretion and 24 h urine protein amounts, GSP, TC, TG, HDL-C and LDL-C, urea nitrogen and creatinine levels in serum of db/db diabetic mice by comparison with db/m mice. In conclusion, Ophiopogonis japonicas oligosaccharide exerts remarkable hypoglycemic and protective effects in db/db mice, thus showing its potential for use in the treatment of type 2 diabetes mellitus.