Objective：To study the effect of bone marrow mesenchymal stem cells（BMMSCs） transplanted into corpus cavernosum on improving erectile dysfunction in diabetic rats. Methods：BMMSCs were separated and cultivated in vitro，then were identified by morphological method and flow cytometry. The diabetic rat model was constructed by intrapertoneal injection of streptozotocin（STZ），then model of diabetes mellitus induced erectile dysfunction（DMED） was sieved by apomorphine（APO）. BMMSCs（2×106 pieces） were transplanted into the corpus cavernosum of the rats in DMED model. Two weeks later，the intracorporeal pressure（ICP） and mean arterial blood pressure（MAP） of normal group，diabetic group and treatment group were determined respectively，the surviving and dif－ferentiation of BMMSCs in corpus cavernosum was observed，vessels in corpus cavernosum were counted after staining the tissue by hematoxylin and eosin. Results：The separation and culture of BMMSCs as well as the construction of the rat model with diabetic erectile dysfunction were successful. Many BMMSCs survived in diabetic group under microscope after being transplanted. The results of erectile function test indicated that the ratio of ICP against MAP was higher in treatment group than in diabetic group. There were more vessels in the treatment group[（12.75±1.89） radices/HP] than in diabetic group[（8.05±1.43） radices/HP]. Conclusion：BMMSCs can improve erectile function of diabetic rat.