Objective To investigate the protective effect of etomidate (Eto) mediated via the Toll-like receptor 4 (TLR4) pathway on acute lung injury in septic shock rats. Methods 75 rats were randomly divided into sham operation, model, model-lipopolysaccharide (LPS), model-Eto and model-Eto-LPS group with 15 rats in each group. Except for the sham operation group, the other groups underwent cecal ligation and perforation to establish the septic shock model. The sham operation group only underwent a laparotomy. 30 minutes before surgery, the model-LPS group was intraperitoneally injected with 15 mg / kg LPS, the model-Eto group was intraperitoneally injected with 60 mg / kg etomidate, and the model- Eto-LPS group was intraperitoneally injected with 60 mg / kg etomidate and 15 mg / kg LPS, model and sham operation groups were intraperitoneally injected with saline. The level of serum endotoxin (ET) and the levels of IL-1β, IL-6 and TNF-α in BALF were measured at 5 hours after the operation. Pathological changes were observed in lung tissue. mRNA and protein expression of TLR4, myeloid differentiation factor (MyD88), and nuclear factor-κB p65 (NF-κB p65) was detected in lung tissue. Results Compared with the sham operation group, ET contents and IL-1β, IL-6 and TNF-α levels in BALF were higher in the model, model-LPS, model-Eto and model-Eto-LPS groups, in the order of model-Eto grouP< model-Eto-LPS grouP<model grouP<model-LPS group (P<0. 05). HE staining showed that alveoli of model and model-LPS were obviously congested, the alveolar wall and lung interstitium had thickened, and a large number of inflammatory cells had infiltrated. The model-LPS group had more severe lesions. In model-Eto and model-Eto-LPS groups, the lesions were relieved with occasional alveolar capillary congestion, and inflammatory cell infiltration. The reductions were more obvious in the model-Eto group. Compared with the sham operation group, the relative expression of TLR4, MyD88 and NF-κB p65 mRNA and protein in lung tissues were higher in model, model-LPS, model-Eto and model-Eto-LPS groups in the order for model-Eto grouP<model-Eto-LPS grouP<model grouP<model-LPS group (P<0. 05). Conclusions Eto has a protective effect on acute lung injury in septic shock rats, which may play a regulatory role by inhibiting the TLR4 pathway.