In order to explore the effect of glial cell line derived neurotrophic factor (GDNF) on the motor neurons of the spinal cord, the present study investigated the localization of GDNF in the lumbar segment of the spinal cord on postnatal 1、3、7、10、14 and 28 days in rats with immunohistochemical staining method. The results showed that the positive GDNF immunoreactivity was present in the motor neurons of the ventral horn on postnatal 1、7 and 28 days, the motor neurons on postnatal 3 days were also weakly stained in rats,and some neurons of the dorsal horn and some glial cells had positive immunoreactivity. Furthermore, GDNF was found in the glial cell of the dorsal root in all groups of the postnatal spinal cord. The present results suggested that GDNF might play important roles in the development and function of the motor neurons of the spinal cord. More experiments should be done to explain why there is no positive immunoreactivity in the motor neurons between postnatal 7 and 28 days.