To investigate the effect and underlying mechanism of adenovirus-mediated antisense ERK2 (Adanti-ERK2) gene therapy upon chronic allograft nephropathy (CAN) of rats, male Lewis (LEW, RT11) rats received male Fisher (F344, RT11v1) renal allografts. The recipients were divided into three groups: (1) empty control group; (2) vector control group; (3) gene therapy group. All recipients were sacrificed for the grafts and serum analysis at the 24th week after transplantation. Morphometric analysis was used to determine the fibrosis of grafts. Immunohistochemistry was used to detect the expression of E-Cadherin, Vimentin, TβR I and the infiltration of CD4 T lymphocyte, CD8 T lymphocyte and ED-1 monocytes. Enzyme linked immunosorbent assay (ELISA) was used to detect TGF-β1 in serum. The grafts in the control group and vector control group showed CAN. There was less E-Cadherin in renal tubular epithelial cells in the empty control group but more Vimentin and TβR I. In the gene therapy group, the fibrosis was ameliorated and fewer T lymphocytes and ED-1 monocytes infiltrated in the interstitium. There was no significant difference in the expression of E-Cadherin between the gene therapy group and normal rats. Compared with the empty control group, the expression of TGF-β1 in the gene therapy group was down-regulated. Adanti-ERK2 gene therapy protects the renal allograft and attenuates graft fibrosis, which may be correlated with a decreased renal tubular epithelial mesenchymal transition, a decreased infiltration of CD4 T lymphocyte, CD8 T lymphocytes and ED-1 monocytes in renal interstitium, and the down-regulated TGF-β1 expression.