To evaluate the hypoglycemic effect of Inonotus obliquus in vivo and to explore its material basis for effective intervention in hyperglycemia. The diabetic mice model was established by high-fat diet combined with intraperitoneal injection of STZ. The changes of body mass and fasting blood glucose were compared before and after intervention. Glucose tolerance experiments were performed on mice in different treatment groups. In order to explore the effects of different extracts of Inonotus obliquus on glucose and lipid metabolism and oxidative stress in diabetic mice， changes in the content of serum total cholesterol， triglycerides， high-density lipoprotein， low-density lipoprotein， glycated serum protein， malondialdehyde， catalase， and superoxide dismutase in liver tissue were determined. On this basis， the inhibition of α-glucosidase by the water extracts of Inonotus obliquus was carried out in vitro. The results showed that both water extracts and alcohol extracts of Inonotus obliquus had certain hypoglycemic effects in vivo， and the effect of water extracts was better than that of alcohol extracts. In vitro enzyme inhibition experiments showed that the water extracts had a much higher inhibition rate of α-glucosidase than that of the positive drug acarbose. The water extracts of Inonotus obliquus can be used as a functional factor to effectively interfere with hyperglycemia and the polysaccharide component is the material basis for exerting hypoglycemic effect， and its possible mechanism of hypoglycemia is a good inhibitory effect on α-glucosidase.