Objective To investigate mRNA and protein expressions of TGF-β1 and their signifi-cance in injured spinal cord after transplantation of activated microglia. Methods Wistar rat model of spinal cord injury was made by using modified Allen's method. Then, the activated microglia was trans-planted into spinal cord injury models tu detect mRNA and protein expressions of TGF-β1 in the spinal curd. Results The mRNA and protein expressions of TGF-β1 in control group were significantly lower than that in test group (P<0.05). Conclusion Transplantation of activated microglia to the impaired spinal cord in rats can increase the mRNA and protein expressions of TGF-β1. The up-regulated expres-sion of TGF-β1 in spinal cord may play a role in promoting the recovery of spinal cord, when the activated microglia may be the main saurce of TGF-β1.