Abstract: Objective To explore the profibrotic effects of chronic aspiration of chenodeoxycholic acid (CDCA) in rats and underlying mechanisms. Methods A rat model of pulmonary fibrosis was established by multiple intratracheal injection of CDCA. Rats treated with 0.5‰DMSO were set as a control group. On Weeks 2, 4, 6 and 8, the profibrotic effects of CDCA were assessed at different stages. Results Compared with the control group, rats in the CDCA modeling group showed disordered alveolar structure and inflammatory cell infiltration in the alveolar space on Week 2. Compared with those on Week 4, inflammatory infiltration significantly relieved on Week 6, with proliferation of plenty of fibroblasts and the formation of pulmonary fibrosis scars. According to Masson staining, the blue area of collagen fibers in the interstitium remarkably increased on Weeks 2, 4, 6, and 8. After Week 6, the scores of inflammation and fibrosis obviously increased in the CDCA group than those in the control groups (P<0.05). The levels of α-smooth muscle actin (α-SMA), hydroxyproline (HYP), transforming growth factor-β1 (TGF-β1), and matrix metallopeptidase-9 (MMP-9) were remarkably up-regulated after Week 6 in rat lungs in the CDCA group,while the content of malondialdehyde(MDA) and the activity of superoxide dismutase (SOD) were gradually down-regulated compared with those in the control group (P<0.05). Conclusions The rat model of chronic aspiration of CDCA is successfully established, with pulmonary fibrosis is most obviously after Week 6, which may be associated with the TGF-β1-ROS pathway.