Abstract: OBJECTIVE To investigate the effects of rehmannia glutinosa oligosaccharide(ROS) on glucose and blood lipid metabolisms and protective effects on liver in type 2 diabetic rats. METHODS Fifty-two male SD rats were fed with high fat and sugar for 8 weeks. After that they were injected with streptozotocin(STZ) to form diabetic model rats. The modeled rats were divided into model group, low, middle, high dose of ROS groups, and metformin group. Another 8 SD rats were selected and fed with normal food as the control group, and injected with equal-volume critric acid buffer solution. On the 0, 2, 4, 8 weekend, the level of blood glucose was determined, Blood lipid levels and fast insulin (FINS) were measured. The concent of malondialdehyde (MDA) and the activity of superoxide dismutases (SOD) and glutathione peroxidase (GSH-PX) of liver tissue were determined in killed rats. Morphological change was examined by HE staining. Liver ultrastrure was determined by TEM. RESULTS Compared with the model group, the levels of FBG, TC, TG, LDL-C, FINS obviously decreased, HDL-C significantly increased, the activity of SOD and GSH-PX increased, MDA decreased significantly in the liver tissues in high, middle dose of ROX groups. HE staining showed that liver fatty degeneration was significantly reduced in ROS groups. TEM results showed that: ROS high-dose group showed mitochondrial structure clear and endoplasmic reticulum in tegrity. CONCLUSION These results suggest that ROS can reduce blood sugar, lipids levels in diabetic rats, relieve fatty degeneration of liver cells, and its mechanism may be related to antioxidation and attenuating liver injury induced by dabete.