Objective To evaluate the effect of genistein on metabolism index in diabetic mellitus(DM) rats,including blood sugar, serum insulin, serum lipid, renal function, etc, and their kidney pathology. Methods 45 healthy male Spraque-Dawley rats were divided into control group (10 rats,free diet),DM group (four weeks:9;eight weeks:8; free diet),DM Gen group (four weeks:10; eight weeks:8; free diet gensitein of 30 mg/kg/day). DM model was made by intraperitoneal injection of streptozotocin(60 mg/kg).Four weeks and eight weeks after, the rats were fasted for 12 hours,then were killed. Blood sugar, serum insulin, serum lipid, renal function were assayed; rat kidneys were examined histopathologically. Results Genistein could decrease the level of blood sugar, cholesterol, improve insulin sensitivity, and also could decrease the level of urea nitrogen and creatinine. Besides, genistein could relieve glomerulus hypertrophy and renal tubular dilatation. Conclusions Genistein can improve the glyeolipid metabolism disorder of diabetic mellitus rats,relieve the changes of renal pathology, improve renal function,and delay the progression of diabetic nephropathy.