Abstract: Objective To investigate the effects of emulsified isoflurane preconditioning on LPS-induced acute lung injury in rats. Methods Acute lung injury was induced by the administration of LPS 8 mg/kg intravenously in male Sprague-Dawley rats. The ratswere randomly assigned to 4 groups:LPS-induced acute lung injury group (LPS, n=10); emulsified Isoflurane Preconditioning group (EISO, n=10); Intralipid pre-treated group (INT, n=10), and saline pre-reated control group (CON, n=5). In the later 3 groups, 2 mL/kg NS, IL and EISO were infused intravenously for 30 min before the administration of LPS respectively. The animals were then observed for 5 hours. The mean arterial blood pressure(MAP) and heart rate(HR) were monitored hourly. Arterial blood gas(ABG) was measured for oxygenation index(OI) at the end of 5h. The blood samples were taken for the measurements of plasma tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6). The lungs were removed for the measurements of wet/dry (W/D) weight ratio, as well as the levels of malondialdehyde (MDA), superoxide dismutase(SOD),myeloperoxidase(MPO). Results The OI of group CON was 435±30,group LPS 225±49,group EISO 367±41,and group INT 267±41. Compared with group CON, OI and pulmonary SOD activity significantly decreased while plasma TNF-α,IL-6 concentration and pulmonary MDA level, MPO activity increased in LPS, EISO and INT groups. The plasma TNF-α,IL-6 concentration, pulmonary MDA level and pulmonary MPO activity of group EISO were lower while OI and pulmonary SOD activity were higher than those of group LPS. Conclusion The emulsified isoflurane pretreatment can ameliorate LPS-induced acute lung injury in rats.