The aim of this study is to investigate the protective effect and mechanism of Brassica rapa L. acidic polysachharide-1 (BRAP-1) on lipopolysaccharide (LPS)-induced lung injury in mice.LPS-induced lung injury mouse model was established for BRAP-1 intervention,and the levels of myeloperoxidase(MPO),malondialdehyde(MDA) and H₂O₂ in alveolar lavage fluid of mice were detected by biochemical reagents.Western blot was used to detect the protein expression levels of protein kinase B(AKT),phosphatidylinositol-4,5-bisphosphate 3-kinase(PI3K),extracellular regulated protein kinases(ERK) phospho-protein kinase B(p-AKT) and B-cell lymphoma-2-associated X protein(BAX),apoptosis-related Cleaved Caspase-3,B-cell lymphoma-2(BCL-2) in lung tissue.The results showed that compared with the model group,BRAP-1 reduced the expression levels of MDA,MPO,H₂O₂ in alveolar lavage fluid and PI3K,AKT protein in lung tissue,as well as the expression levels of apoptosis factor BAX and apoptosis key factor Cleaved Caspase-3 protein,and enhanced the expression level of anti-apoptotic factor Bcl-2 protein.In conclusion,BRAP-1 can play a protective role by scavenging free radicals in lung tissue of mice with lung injury,inhibiting oxidative stress and regulating apoptosis of lung tissue cells.