Objective To investigate the influence of fasudil on the epithelial-mesenchymal transdifferentiation of renal tubular epithelial cells in diabetic rats and to explore the mechanism. Methods Wistar rats were randomly divided into three groups: control, diabetes and fasudil-treatment. All the rats were sacrificed after three months of feeding with or without fasudil. Pathological changes of the glomeruli and renal interstitium were studied by periodic acid-Schiff’s staining and Masson staining, respectively. Expression of ROCKI, α-SMA, E-cadherin and the distribution of β-catenin was examined by immunohistochemistry. Changes in the MYPT1 phosphorylation profile and α-SMA, E-cadherin and membrane β-catenin expression were detected by Western blot. Changes in the levels of ROCKI, E-cadherin and total β-catenin mRNA expression were analyzed by real-time PCR. Results Fasudil treatment notably attenuated renal interstitial fibrosis in diabetic rats. Compared to the control rats, diabetic rats showed an elevated phosphorylation of MYPT1 (P<0.01）, increased expression of α-SMA (P<0.01), decreased expression of E-cadherin and membrane β-catenin (P<0.01, respectively) and increased expression of ROCKI, total β-catenin mRNA(P<0.01, respectively）, decreased expression of E-cadherin mRNA（P<0.01）. Fasudil treatment for diabetic rats attenuated MYPT1 phosphorylation (P<0.01）, decreased α-SMA expression（P<0.01), increased E-cadherin and membrane β-catenin expression （P<0.01, respectively), and reduced ROCKI, total β-catenin mRNA expression (P<0.01, respectively), increased expression of E-cadherin mRNA (P<0.01). Conclusions Fasudil may reduce the epithelial-mesenchymal transdifferentiation and renal interstitial fibrosis in diabetic rats through the inhibition of ROCK activity. Such effect further facilitates the recovery of the cell-cell adhesion among renal tubular epithelial cells and the formation of adhesion complex.