Western blot analysis and immunohistochemistry revealed the increased expressions of the phosphorylated Smad3 (p-Smad3) and the reduction of Smad7 in the renal tissues of diabetic nephropathy mice, which was companied with the upregulated expressions of E3-ligase Arkadia and phosphorylated NF-κB/p65 (p-p65) in the renal tissues. This evidence concerns the gene SMAD3 and diabetic kidney disease.