Abstract： Objective To study the foxml gene and its protective effect on the lung tissue of rats with acute lung injury (ALI) induced by lipopolysaccharide (LPS), and to observe the dexamethason' s (DEX) impacts on foxml gene and the prognosis of ALI. Method Seventy-two healthy mice were randomly(random number) divid-ed into three groups: control group (A group, n = 24), model group (B group, n = 24) and DEX treatment group (C group, n = 24). The observing intervals were respectively set in 24 h, 48 h and 72 hours. At each ob-serving interval, the foxml protein in lung tissue of mice was detected by using immunohistochemistry (IHC), and the expression of foxml gene in lung tissue was detected by using RT-PCR, as well as to observe the pathological changes in lung tissue. Results Comparisons were made between paired groups at 24 h,48 h and 72 h intervals in which the expression of foxml mRNA and the level of foxml protein in lung tissue of mice in C group were signifi-cantly higher than those in B group (P < 0.05), and those in B group were significantly higher than those in A group (P < 0.05). The expression of foxml mRNA and the level of foxml protein in lung tissue of mice in B group at 48 h interval were significantly higher than those both at intervals of 72 h and 24 h (P < 0.05), and the those at 72 interval were significantly higher than those at 24 h interval (P < 0.05). Compared with B group, the pathologi-cal changes in lung tissue of mice in C group were lessened. Conclusions In both model group and dexamethasone treatment group, the expression of foxml mRNA and the level of foxml protein in lung tissue of mice are increased significantly. Dexamethasone lessens the injury of both vascular endothelial cells and alveolar epithelial ceils of lung tissue, and it also significantly increases the expression of foxml mRNA and the level of foxml protein.