Abstract: To provide experimental data and theory basis for treatment of male infertility in diabetics, a combination of sildenafil and L-carnitine was applied on male rates with diabetes mellitus(DM). Adult male Sprague-Dawley rats were treated with streptozotocin(STZ)to induce type 2 diabetes model. Then, DM rats were then treated with sildenafil, L-carnitine, and the combination of sildenafil and L-carnitine respectively. The sperm indexes, endocrine hormones and oxidative stress of DM rats were analyzed and evaluated. As a result, the combination of sildenafil and L-carnitine had better ameliorated the sperm indexes, endocrine hormones and oxidative stress than L-carnitine or sildenafil alone. It was found that sildenafil and L-carnitine can improve the sperm quality, inhibit spermatogenic cell apoptosis, increase the gonadal hormone levels and relieve the oxidative stress in diabetes-induced erectile dysfunction rats. Furthermore, it was firstly confirmed that the use of the combination of sildenafil and L-carnitine is more beneficial for treatment of DMED through their own antioxidant and hormone regulation properties as compared to the use of sildenafil or L-carnitine alone.