Opuntia humifusa known as the Eastern prickly pear have been used as a treatment of burns, diarrhea, asthma, rheumatism, gonorrhea, and diabetes in alternative medicine. O. humifusa is widely cultivated in the middle and southern provinces of Korea and distributed in North America. The aim of this study is to investigate anti-diabetic effect of O. humifusa stem (OHS) water or 80% MeOH extract using 3T3-L1 adipocytes and db/db mice animal models. OHS 80% MeOH extract at a dose of $250{mu}g/ml$ significantly increased the glucose uptake and lipid accumulation compared with the control in 3T3-L1 adipocytes. Blood glucose, plasma total cholesterol and triglyceride levels were significantly reduced by oral treatment of OHS 80% MeOH extract (200 mg/kg BW) for 6 weeks in db/db mice. Also, the oral treatment of OHS 80% MeOH extract slightly changed the plasma insulin and insulin resistance levels in db/db mice, but were no significance in comparison to control. Glucose transporter(GLUT)4 expressions of adipose tissue and muscle were significantly increased more than that in the control. Therefore, these results suggest that OHS 80% MeOH extract inhibits the blood glucose level through regulation of lipid profile, insulin resistance, and GLUT4 expression in db/db mice and its diabetic effect is effective more than water extract.