Idiopathic pulmonary fibrosis (IPF), a chronic, progressive and irreversible disease, needs long‐term treatment. Bicyclol was found to play a great role in pulmonary fibrosis, and the present study is to explore how bicyclol affects IPF with the involvement of microRNA‐455‐3p (miR‐455‐3p) and Bax. Bleomycin (BLM) was used to induce the IPF model in Sprague‐Dawley rats to detect the expression of miR‐455‐3p, Bax, and B‐cell lymphoma factor 2 (Bcl‐2). Moreover, to further investigate the mechanisms of bicyclol, the BLM‐induced fibrotic cell model was used after the lung epithelial cells HPAEpiC received miR‐455‐3p knockout treatment. The rats were then treated with vehicle and bicyclol, respectively. The apoptosis of fibrotic cells and Bax/Bcl‐2 were identified. Inhibition function of bicyclol was optimal at a dose of 150 mg/kg. Bicyclol inhibited cell apoptosis and reduced Bax/Bcl‐2 expression in rats. miR‐455‐3p could potentially bind to Bax gene. Bicyclol reduced the levels of methylenedioxyamphetamine, superoxide dismutase, and glutathione in rat lung tissue, inhibited the apoptosis of rats with IPF and upregulated miR‐455‐3p expression. In vitro studies showed that bicyclol significantly promoted miR‐455‐3p expression in HPAEpiC fibrosis. Bicyclol inhibited fibrosis‐induced apoptosis of HPAEpiC in alveolar epithelial cells through promoting miR‐455‐3p, which inhibited Bax expression in IPF. Bicyclol may suppress the apoptosis of alveolar epithelial cells by upregulating miR‐455‐3p. This study laid a theoretical foundation for further understanding of IPF and searching for new molecular therapeutic targets.