Objective To study the mechanism of alleviating lung ischemia-reperfusion injury by postischemic treatment with namefene hydrochloride, and explore the optimal timing of drug treatment throughout the disease course. Methods A total of 60 rats were randomly divided into six groups with 10 rats in each group: a sham group, a model group, a nalmefene A (NA) group, a nalmefene B (NB) group, a nalmefene C (NC) group and a nalmefene D (ND) group. The sham group without drug treatment was not treated with ischemia-reperfusion. The lung ischemia-reperfusion model was established by occlusion of the left pulmonary hilum in the model group without drug treatment. After ischemic treatment, the NA, NB, NC and ND groups were respectively injected with nalmefene (15 μg/kg) by the tail vein at 5 min before, 10 min, 30 min and 60 min after pulmonary circulation reperfusion. At the 3rd hour after reperfusion, all rats were sacrificed and the specimens from the upper lobe of the left lung tissue were preserved to observe pulmonary lesions, detect wet/dry weight ratio and the activity of myeloperoxidase (MPO), the expressions of tumor necrosis factor-α (TNF-α), Toll-like receptor 2 (TLR2) mRNA and MyD88 mRNA as well as the expressions of TLR2, MyD88, NF-κB p65 and p-NF-κB p65 in lung tissue. Results There were different degrees of alveolar septal destruction, obvious pulmonary interstitial edema, the infiltration of inflammatory cell, the exudationred of blood cell in the mesenchyme, and the collapse of partial alveolar in the model group and the NA, NB, NC, ND groups. In terms of wet/dry weight ratio, the score of lung tissue injury, the activity of MPO, the expressions of TNF-α, TLR2 mRNA and MyD88 mRNA as well as the expressions of TLR2, MyD88, NF-κB p65 and p-NF-κB p65 in lung tissue, the model group were significantly higher than the sham group (P<0.01); there was no significant difference between the ND group and the model group (P>0.05). The corresponding test values of the nalmefene groups with post-ischemic treatment showed the characteristics of ND group> NC group> NB group> NA group (P<0.01). Conclusion The effect of nammefene on alleviating lung ischemia-reperfusion injury is closely related to the inhibition of TLR2, MyD88, NF-κB p65 and phosphorylation of NF-κB p65 with a characteristic of time-dependent manner.