Abstract: OBJECTIVE To investigate the interventional effectiveness and the relevant mechanisms of bicyclol on bleomycin-induced pulmonary fibrosis(BPF) in rats. METHODS The male SD rats were randomly divided into 5 groups:control group, model group, low, medium and high dose of bicyclol groups, 10 rats per group. In addition to the control group, the other four groups were established to the pulmonary fibrosis model by bleomycin intra-tracheal injection. After 24 h of successful model, the different dose groups of bicyclol were intragastrically administered with different doses of dissolved bicyclol tablets, the control group and the model group were injected with equal volume of saline under the same conditions. All groups were observed the general condition, according to the survival rate of rats in different dose groups of bicyclol, the group with the highest survival rate, the control group and the model group were selected for the next experiment. The remaining 3 groups of rats continued to be tested lung tissue pathology, Ashcroft scores, alveolar septal thickening measurement and the expression of pro-caspase 3, cleaved caspase 3, Bcl-2 and Bax of lung tissue.RESULTS The high dose of bicyclol group had the highest survival rate in all model groups(P<0.05). So the experiment was continued in the high dose of bicyclol group(bicyclol group). Compared to the model group, the degree of alveolar structure destruction and pulmonary interstitial fibrosis, pulmonary fibrosis Ashcroft's scoring were significantly reduced in bicyclol group(P<0.01), and the alveolar septal thickening was significantly thinner(P<0.01) and the expression of the Bax and cleaved caspase 3 decreased significantly (P<0.01), but the Bcl-2 was increased(P<0.01).CONCLUSION Bicyclol have significant protect effcet on BPF rats, the potential mechanism may be related to interfere with Bcl-2, Bax and cleaved caspase 3 to influence cell apoptosis for improving pulmonary fibrosis.