ObjectiveTo study effects of two kinds of epidermal growth factor receptor kinase inhibitors on bleomycin-induced pulmonary fibrosis in mice, and regulation mechanism on oncostatin M (OSM) and downstream signaling pathways.MethodsForty Kunming female mice were randomly divided into a control group, a fibrosis group, a gefitinib group, and an erlotinib group. The mice in the control group were administered with saline aerosol intratracheally. The mice in the fibrosis group were administered with bleomycin at a dose of 3 mg/kg aerosol intratracheally. The mice in the gefitinib group and the erlotinib group were administered with bleomycin at a dose of 3 mg/kg aerosol intratracheally and then gastrically perfused with gefitinib (20 mg·kg–1·d–1) or erlotinib (25 mg·kg–1·d–1). All mice accepted computer tomography examination 14 days after the treatment and then were sacrificed, and the lungs were collected for further detection. The lungs were stained with hematoxylin eosin and Masson’s trichrome, examined with Western blot for pathological examination and expressions of α-smooth muscle actin (α-SMA), OSM, Janus kinase 1 (JAK1), phospho-JAK1 (p-JAK1), signal transducers and activators of transcription 3 (STAT3), and phospho-STAT3 (p-STAT3) proteins.ResultsThe pathological injury of the lung in the gefitinib group and the erlotinib group was significantly relieved compared with that in the bleomycin group. The expressions of α-SMA, OSM, p-JAK1/JAK1, and p-STAT3/STAT3 proteins were also significantly reduced. There were no differences between the above-mentioned indexes between the gefitinib group and the erlotinib group.ConclusionsGefitinib and erlotinib can significantly relieve bleomycin-induced pulmonary fibrosis in mice. The underlying mechanism may be involved in inhibiting expression of OSM and downstream JAK/STAT pathways.