Since the potential influence and mechanism of gefitinib on pulmonary fibrosis have not been fully studied, the aim of the present research was (1) to detect the model of action between HMGB1 and α-SMA in pulmonary fibrosis and (2) to study the mechanism and resulting effect of gefitinib in the treatment of pulmonary fibrosis. The gene discussed is ACTA1; the disease is pulmonary fibrosis.