Objective A rat model of acute lung injury (ALI) was established by intratracheal instillation of lipopolysaccharide (LPS) and changes in the lung injury were observed at various periods. Methods Thirty-two healthy Sprague-Dawley (SD) rats were randomly divided into normal (n= 8) and model (n= 24) group. In accordance with the duration of LPS infusion, the model group was divided into three subgroups: 3, 6 and 12 h groups, with eight rats in each group. The ALI rat model was established by tracheal instillation of LPS ( 2 mg / kg). Observations included the general performance of rats, gross observation of lungs, detection of lung functions, calculation of the lung wet / dry weight ratio, detection of interleukin ( IL) - 1β, IL-8, and tumor necrosis factor - α in bronchoalveolar lavage fluid, detection of malondialdehyde and superoxide dismutase in lung tissue, and histomorphological observation by hematoxylin-eosin staining in lung tissue. Changes of acute lung injury were also evaluated at different stages. Results After modeling, the survival rate of rats in the model group was 100%. Compared with the normal group, the general performances of rats in the 3 h group were similar with less food intake, less activity, more mucus secretions in the nasal cavity, faster respiratory frequency, and audible wheezing. Gross observation of the lungs showed liver-like degeneration of the lung tissue in the left and right hilum of the lung in the 3 h group, bleeding spots were scattered on the left and right lobes, and the bleeding site was bright red. The pulmonary functions of rats after LPS exposure for 3 h showed significant decreases in the forced expiratory volume (FEV) in 0. 1 s, forced expiratory volume in 0. 3 s, ratio of forced expiratory volume in 0. 1 s to forced vital capacity, and ratio of forced expiratory volume in 0. 3 s to forced vital capacity (P< 0. 05,P<0. 01). The wet / dry weight ratio was increased significantly ( P< 0. 01). The contents of IL-1β, IL-8, and tumor necrosis factor - α in bronchoalveolar lavage fluid were increased significantly ( P< 0. 01). The content of malondialdehyde was increased significantly (P< 0. 01). The content of superoxide dismutase was decreased significantly (P<0. 01). Hematoxylin-eosin staining showed obvious thickening of the alveolar septum, pulmonary interstitial edema, and erythrocyte exudation. Conclusions Tracheal instillation of LPS causes significant decreases in lung functions, severe pulmonary inflammation, an oxidation-antioxidation imbalance, and severe pulmonary edema in rats, which lead to acute lung injury. Furthermore, it is more beneficial to establish an ALI rat model at the 3 h time point.