〔Abstract〕 Objective To investigate the effects of astragalus mongholicus extract ( AME) on lung injury and the myeloid differentiation factor 88 ( MyD88 ) / Toll-like receptor 4 ( TLR4 ) / nuclear factor kappa B ( NF-κB) p65 pathway in rheumatoid arthritis induced interstitial lung disease (RA-ILD) rats．Methods SD rats were randomly divided into a control group，RA-ILD group，low-dose AME group (5 g / L) ，high-dose AME group ( 10 g / L) ，and high-dose AME + lipopolysaccharide (LPS) group ( 10 g / L AME + 1 mg / L TLR4 activator LPS) ．Except for the control group，rats in all other groups were injected with bovine type Ⅱ collagen，Freund ’s complete adjuvant， and bleomycin to establish the RA-ILD model．The arthritis index and lung tissue wet-dry weight ratio of rats were tested．ELISA was applied to detect the levels of inflammatory factors interleukin (IL) -1 β , IL-6 and tumor necrosis factor-α ( TNF-α) in bronchoalveolar lavage fluid． Hematoxylin eosin staining was used to observe pathological changes of rat knee joint tissue and lung tissue．Western blot was applied to detect the expression of autophagy fac- tors Beclin 1，microtubule-associated protein 1A /1B-light chain 3 (LC3) Ⅱ / Ⅰ , and MyD88 /TLR4 /NF-κB p65 pathway related proteins in lung tissue．Results Compared with control group，knee joint tissue and lung tissue of rats in RA-ILD group were damaged，the arthritis index，lung tissue wet-dry weight ratio，levels of IL-1 β , IL-6， and TNF-α , the expression levels of MyD88 and TLR4 proteins ，and p-NF-κB p65 /NF-κB p65 ratio increased (P＜0. 01) ，the expression of Beclin 1 and LC3 Ⅱ / Ⅰ proteins decreased (P＜0. 01) ．Compared with RA-ILD group，the low-dose and high-dose AME groups showed reduced tissue damage in rats，the arthritis index，lung tis- sue wet-dry weight ratio，levels of IL-1 β , IL-6，and TNF-α , the expression levels of MyD88 and TLR4 proteins， and p-NF-κB p65 /NF-κB p65 ratio showed a dose-dependent decrease (P＜0. 05 or P＜0. 01) ，the expression of Beclin 1 and LC3 Ⅱ / Ⅰ proteins showed a dose-dependent increase (P＜0. 05 or P＜0. 01) ．Compared with high- dose AME group，the tissue damage of rats in the high-dose AME + LPS group was worsened，the arthritis index， lung tissue wet-dry weight ratio，levels of IL-1 β , IL-6，and TNF-α , the expression levels of MyD88 and TLR4 pro- teins，and p-NF-κB p65 /NF-κB p65 ratio were higher (P＜0. 01) ，the expression of Beclin 1 and LC3 Ⅱ / Ⅰ pro- teins was lower (P ＜0. 01 ) ． Conclusion AME inhibits the MyD88 /TLR4 /NF-κB p65 pathway and alleviates lung injury in RA-ILD rats．