The immunohistochemical detection of pulmonary fibrosis markers in mice showed that a-SMA, collagen I, fibronectin, and connective tissue growth factor in the lung were significantly increased by a single intratracheal administration of BLM, while the concentration of SIN in the treatment group was negatively correlated with the staining degree of fibronectin. This evidence concerns the gene FN1 and pulmonary fibrosis.