OBJECTIVE：To study the protective effects of autophagy inhibitor 3-Methyladenine（3-MA）against lipopolysaccharide（ LPS）-induced acute lung injury in mice and its mechanism. METHODS：Mice were randomly divided into normal control group，model group（LPS 15 mg/kg），drug control group（3-MA 20 mg/kg），low-dose and high-dose groups（LPS 15 mg/kg+ 3-MA 20，40 mg/kg），with 10 mice in each group. Except for normal control group and drug control group，other groups were given LPS intraperitoneally to induce acute lung injury model，and drug control group and low-dose and high-dose groups were given equivalent dose of 3-MA intraperitoneally 1 h before modeling. 6 h after modeling，lung wet/drug mass ratio（W/D）was determined respectively，and pathology change of lung tissue was observed by HE staining. TNF-α ，NF-κ B p65，LC3B Ⅱ/Ⅰ and Cleaved-caspase-3 protein expression were detected by Western blot. RESULTS：Compared with normal control group，W/D， TNF-α，NF-κB p65，LC3BⅡ/Ⅰ and Cleaved-caspase-3 protein expression increased in model group（P＜0.01）. Compared with model group，W/D，the expression of TNF-α，NF-κB p65，LC3BⅡ/Ⅰ and Cleaved-caspase-3 protein decreased in low-dose group （P＜0.05），white just only LC3BⅡ/Ⅰ protein decreased high-dose group（P＜0.01）. CONCLUSIONS：In LPS-induced acute lung injury model in mice，the excessive autophagy could activate the NF-κB pathway and involve the inflammatory responses and induce lung cells apoptosis. The moderate autophagy inhibition by 3-MA can ameliorate inflammatory response and protect lung tissue.