〔Abstract〕 Objective To explore the inhibitory effect of microRNA-200b(miR-200b) on pulmonary fibrosis in silicotic mice. Methods Male C57BL/6 mice were randomly divided into control group, SiO2group, SiO2+agomir-NC group and SiO2+miR-200b agomir group, with 6 mice in each group. The mice in the SiO2group were instilled intratracheally with 50 μl of saline containing 5 mg SiO2particles. miR-200b agomir and agomir-NC were delivered to mice in the SiO2+miR-200b agomir and SiO2+agomir-NC groups respectively by intratracheal instillation on day 1 and 7 after SiO2exposure. Animals were sacrificed after the lung function test on the 14th day. The pathological changes of lung tissues were observed by HE and Masson staining. Then the concentration of total proteins and the numbers of leukocytes in bronchoalveolar lavage fluid(BALF) were measured. The content of transforming growth factor-β1(TGF-β1) in BALF was detected by ELISA kit. Results Compared with the control group, inflammatory cell infiltration and collagen deposition were observed in the lungs tissues of the mice in the SiO2group and the SiO2+agomir-NC group, while these detrimental effects were weakened in the SiO2+miR-200b agomir group. In addition, compared with the control group, the frequency(f) was accelerated and the number of Pause(PAU) increased(P<0.05), while the ratio rate of achieving peak expiatory flow(Rpef) decreased in the SiO2group and the SiO2+agomir-NC group(P<0.05). After miR-200b agomir intervention, the lung function of silicotic mice was improved. Moreover, miR-200b agomir intervention could also effectively alleviate the increase in the concentrations of total protein, the numbers of total leukocytes and the secretion of TGF-β1 in the BALF of mice induced by SiO2stimulation. Conclusion miR-200b can effectively ameliorate the lung function of silicotic mice and inhibit the progress of fibrosis.