Objective To study the effects of bone marrow mesenchymal stem cells modified by brain-derived neurotrophic factor (BDNF) gene on the repair of spinal cord injury by electrophysiological assay. Methods Thirty healthy Sprague-Dawley rats (male and female) were randomly divided into 3 groups: Blank group, 10 rats (removal of the lamina only and exposed spinal dura mater);spinal cord injury (SCI) group,10 rats;and cell transplantation after SCI group, 10 rats. Eight rats of them were selected randomly and detected their SEP and MEP, and evaluated the degree of recovery of motor scores in the rats at 1 d, 7 d, 14 d, 21 d, 30 d, and 60 d. Result Since 4 days after cell transplantation, the process of hind limbs changes was as follows: at the 1-4 days after injury, the injury side hind limb had flaccid paralysis, mopping the floor walk, the movement of contralateral hind limb was gradually recovered from the initial injury, the injury side hind limb had spastic paralysis in 5-9 days after SCI; during 10-14 days, the injury side had a few activities; the contralateral side recovered to a less normal state; At 15-21 days, activities of the injury side improved obviously, until the 30th day. The activity and muscle tension degree of the injury side recovered most obviously. After 30 days no more obvious improvement was observed. Immunohistochemistry showed that the transplanted mesenchymal stem cells, which were induced and labeled firstly, survived at the damage spinal cord, and behavioral observation found that the cell transplantation improved exercise capacity of the rats injured before. Conclusion Bone marrow mesenchymal stem cells modified by BDNF gene can partially promote the recovery of nerve transmission function and nerve regeneration.