Objective To investigate the protective effect of lycium barbarum polysaccharide(LBP) on oxidative stress in cavernous tissue of diabetic rats. Methods After mating confirmed normal sexual function at 20 months of diabetes of 60 male SD rats were randomly divided into the experimental group (n=30) and control group (n=30), there were 1 rats each died off in the two groups. The rats in the experimental group were subjected to intragastric administration of LBP, and the rats in control group were given the same amount of normal saline. Rats were killed 6 weeks after administration. Experimental rats of two groups were observed in general, including mental status, appetite, drinking, body weight, hair color and other activities. Rat corpus cavernosum tissue superoxide dismutase, malondialdehyde, nitric oxide, nitric oxide synthase were compared between the two groups. Results The rats in control group were aging, polyphagia, polyuria and weight loss, and there was relatively active, strong appetite, good mental state, increased body weight in experimental group. the rat corpus cavernosum superoxide dismutase activity of experimental group was (152.35±8.48) mgprot/mL, significantly higher than the control group (134.42±10.71) mgprot/mL, the MDA content was (5.41±0.26) nmol/mgprot, significantly lower than the control group (6.69±0.95) nmol/mgprot, the difference was statistically significant (P<0.05). Enzyme activity and the content of nitric oxide were observed in the penis of rats were (17.73±1.45) U/mgprot, (6.93±1.18) mol/mgprot, significantly higher than the control group (14.56±1.84) U/mgprot and (4.72±1.49) mol/mgprot, the difference was statistically significant (P<0.05). Conclusions LBP has protective effect on oxidative stress in penile injury in diabetic rats, and oxidative stress injury of erectile tissue by supplement of LBP and improves erectile ability. Key words: Diabetes Mellitus; Penis; Oxidative Stress; Disease Models, Animal; Lycium; Rats