The objective of the present study is to observe the anti-inflammatory and antioxidant effects of Tripterygium wilfordii extract on LPS-induced acute lung injury (ALI) in rats, and to explore its protective mechanism against ALI. And quantitative determination was performed on the extract. 120 rats were randomly divided into normal control group (saline), model group, dexamethasone group (5 mg/kg, ip), and Tripterygium wilfordii extract low-, mediumand high-dose groups (100, 150, 200 mg/kg, ip), n = 20 in each group. The rats were administered for 3 d, 1 h after the last ip administration, ALI model was induced by ip endotoxin (LPS), 6 h later, the rats were sacrificed, BALF WBC count and protein content, nuclear transcription factor (NF-κB) p65 expression in lung tissue, levels of tumor necrosis factor (TNF-α), interleukin (IL)-6, interleukin (IL)-10, superoxide dismutase (SOD), and malondialdehyde (MDA), as well as neutrophil myeloperoxidase (MPO) activity in each group were observed. Total triterpenoid content in Tripterygium wilfordii extract was determined by UV-V is spectrophotometry with tripterine as the reference. Compared with the control group, in the Tripterygium wilfordii extract medium- and high-dose groups, lung tissue NF-κB p65 expressions were (38.03 ± 4.19)% and (30.69 ± 3.99)%, MDA levels were (1.76 ± 0.21) and (1.36 ± 0.12) nmol/mg, TNF-α levels were (263.66 ± 39.65) and (210.78 ± 30.25) μg/L, IL-6 levels were (289.47 ± 99.99) and (226.58 ± 96.25) ng/L, and MPO activities (2.76 ± 0.54) and (2.43 ± 0.42) U/g, all of which were significantly lower (P<0.05~P<0.01) than those of the model group; IL-10 levels were (17.89 ± 3.89) and (17.29 ± 3.68) μg/L, SOD levels were (69.47 ± 9.23) and (73.65 ± 8.12) U/mg, BALF WBC count and protein content in the model group significantly increased (P<0.05~P<0.01); all of which were significantly higher (P<0.05~P<0.01) than those of the model group. Total triterpenoid content in Tripterygium wilfordii extract was 27.379. Tripterygium wilfordii extract can decrease the pulmonary vascular permeability caused by LPS-induced ALI, reduce inflammation exudation, and lower the degree of oxidative stress injury.