Objective：To investigate the mechanism of diabetic erectile dysfunction（ED） by detecting the variation of the activity and distribution of nuclear factor-kappaB（NF-κB） in the corpus cavernosum of rats with diabetes mellitus. Methods：All of 40 male Sprague-Dawley rats were divided into 3 groups：control group（group A, n = １０）， diabetic group for 4 weeks（group Ｂ, n = １4）， and diabetic group for 12 weeks（group C, n = 16）. The diabetes model was established by the injection of STZ. After some weeks erection function was examined by apomorphine injection. The content of NF-κB in the erectile tissue was evaluated by immunohistochemistry staining. At the same time the activity of NF-κB was detected by electrophoretic mobility shift assay（EMSA）. Results：Compared with those in group A，erection function was down-modulated significantly， and the activity of NF-κB in penile tissues was higher in group B and group C（P < 0.05）. And the expression of NF-κB had an increasing tendency with the extension of the disease course. NF-κB was mainly expressed in the endothelial cell of the corpus cavernosum， however less in contractile fiber cells and other cells. Conclusion：The activity and distribution of NF-κB in the corpus cavernosum of diabetic rats has been shown to be altered with diabetes. NF-κB might play an important role in the develoment of diabetic ED.