Aim To investigate the effects of ganoderma lucidum polysaccharide on endothelial function of type 2 diabetic rats in vivo,and explore the potential mechanisms of ganoderma lucidum polysaccharide on protecting the endodermis of blood vessel. Methods SD rats were fed with high fat diet for 4 weeks,then injected STZ(30 mg/kg) to replicate type 2 diabetic rats.The successful diabetic rats model were randomized into normal control group,diabetes group,berberine(30 mg/kg) in the positive control group,ganoderma lucidum polysaccharide of low,middle and high-dose group(Ganoderma lucidum polysaccharide were orally given 200 mg/kg,400 mg/kg and 800 mg/kg).After 16 weeks' treatment,the thoracic aorta was immediately isolated.Endothelium-dependent relaxation induced by acetylcholine,the activity of catalase(CAT),glutathione peroxidase(GSH-PX),total cholesterol(TC) and triglycerides(TG) in serum were detected. Results After treatment the blood glucose concentration of middle-dose group and high-dose group was lower than diabetes group(P<0.01).The advanced glycation end product(AGE) in serum was significantly lower in high-dose group than diabetes group(P<0.01),catalase and glutathione peroxidase in serum was significantly higher in high-dose group than diabetes group(P<0.01),TC and TG in serum was significantly lower in high-dose group than diabetes group(P<0.01). Conclusion Ganoderma lucidum polysaccharide is able to protect against aorta endothelial dysfunction in diabetic rats.The mechanisms may be involved in decreaseing advanced glycation end products in serum,enhancing the activity of CAT and GSH-PX in serum and accommodating dyslipidemia.