Abstract: OBJECTIVE To investigate the hypoglycemic effect of Yin Sang Granules (YSG) on db/db mice model of spontaneous type 2 diabetes mellitus. METHODS The db/db mice were randomly divided into 5 groups: model group， metformin group， YSG low dosage group， YSG middle dosage group and YSG high dosage group， and these db/m mice were selected as normal group. Fasting blood glucose (FBG) was measured in the first 7 weeks. Oral glucose tolerance tests (OGTT)， insulin tolerance test (ITT) and starch tolerance test (STT) were measured separately at the 9th， 10th and 11th week. The contents of hepatic glycogen， insulin (INS)， glycosylated haemoglobin (GHb)， glycated serum protein (GSP)， total cholesterol (T-CHO)， triglyceride (TG)， high-density lipoprotein cholesterol (HDL-C)， low-density lipoprotein cholesterol (LDL-C) were detected at the 12th week. Pathological change of kidney and pancreas were observed with hematoxylin-eosin staining. RESULTS Compared with the model group， the blood glucose of OGTT， ITT and STT of the YSG groups were significantly decreased (P<0.05~0.01)， and the area under the curve was also decreased (P<0.05~0.01). The hepatic glycogen， HDL-C of the mice in YSG groups were significantly increased (P<0.05~0.01)， and the levels of FBG， GSP， INS， GHb， T-CHO， TG， LDL-C were significantly decreased (P<0.05~0.01). Moreover， the results of pathological section showed that the degree of degeneration of the renal tubular epithelial cells and renal pelvis expansion were reduced， and the margin of islet cells was more regular and its vacuole degeneration was alleviated. CONCLUSION YSG adjusted synthetically the hyperglycemia and dyslipidemia in db/db mice by improving insulin sensitivity.