The aim of this study is to evaluate the antifibrotic effect of ring-type Sp1 decoy oligonucleotides (ODNs) through blocking the transcription of transforming growth factor (TGF)-beta1 and its downstream target genes. In this experiment, the expression of TGF-beta1, metalloproteinase (MMP)-13, and fibronectin was decreased in the group with the treatment of the ring-type Sp1 decoy ODNs. Also, alpha-smooth muscle actin positive bronchial lining cells and alveolar epithelial cells were observed, especially around the lesions of extracellular matrix (ECM) deposition. These findings provide evidences for the finding of pulmonary epithelial-mesenchymal transition (EMT) and the effectiveness of Sp1 transcription factor as a target for the gene therapy on lung fibrosis.