Objectives: We performed this study to compare the antidiabetic effects of Coptidis Rhizoma (CR) and its major component berberine with gliclazide. Materials and Methods: Diabetic rats induced by injection of streptozotocin (STZ) 55mg/kg were treated with CR 100, 200, 400mg/kg and berberine 100mg/kg. After rats were treated for 5 days, serum glucose, total cholesterol, triglyceride, BUN, creatinine and antioxidant levels were determined. Results: The cytotoxic effects of CR (0.1, 0.01, and 0.001mg/mL), berberine and gliclazide ($0.1{mu}M$, $1{mu}M$, and $10{mu}M$) were tested in rat insulinoma (RIN) cells induced with 5mM STZ. The levels of fasting blood glucose, total cholesterol, triglyceride, BUN and creatinine of CR and berberine treated groups were reduced as much as that of gliclazide group in comparison to control groups, whereas total antioxidant levels increased. In vitro experiments showed that CR and berberine have a cytoprotective effect on RIN cells.