To describe the relationship between miRNA-21 and renal fibrosis.Methods NRK-52E cells cultured in vitro,then constructed fibrosis model induced by transforming growth factorβ1 ( TGF-β1 ) , then bone morphogenetic protein-7 ( BMP-7 )-containing lentivirus vector was used to transfect the NRK-52E cells to anti-fibrosis, SMAD1, SMAD6, FN1, rno-miR-21-5p gene expression were detected.Results After TGF-β1 treatment, the BMP-7 mRNA and protein expressions were significantly decreased, FN1 mRNA and protein expressions were significantly increased ( P<0.05 ) . After transfected by BMP-7-containing lentivirus vector, BMP-7 mRNA expression significantly increased(P<0.05), FN1, SMAD6 and rno-miRNA-21-5p mRNA decreased, SMAD1 mRNA increased(P<0.05).Conclusion Epithelial-to-mesenchymal transition (EMT) is positively correlated with the miRNA21 and TGF-beta 1, its maybe related to the changes of BMP-7, SMAD1 and SMAD6.