Abstract： Background Paraquat (PQ), an effective and widely used herbicide, has been proven to be safe when appropriately applied to eliminate weeds. However, PQ poisoning is an extremely frustrating clinical condition with a high mortality and with a lack of effective treatments in humans. PQ mainly accumulates in the lung, and the main molecular mechanism of PQ toxicity is based on redox cycling and intracellular oxidative stress generation. The aim of this study was to evaluate whether lysine acetylsalicylate (LAS) could protect the lung from the damage of PQ poisoning and to study the mechanisms of protection.Methods A model of PQ poisoning was established in 75 Sprague-Dawley rats by intragastric administration of 50 mg/kg PQ, followed by treatment with 200 mg/kg of LAS. The rats were randomly divided into sham, PQ, and PQ+LAS groups, with 25 in each group. We assessed and compared the malonaldehyde (MDA) content, superoxide dismutase activity (SOD), glutathion peroxidase (GSH-Px), and catalase (CAT) in serum and lung and the hydroxyproline (HYP)content, pathological changes, apoptosis and expression of Bcl-2/Bax protein in lung of rats on days 1, 3, 7, 14 and 21after PQ poisoning and LAS treatment.Results Compared to the PQ group rats, early treatment with LAS reduced the MDA and HYP contents, and increased the SOD, GSH-Px, and CAT activities in the serum and lung on days 1, 3, 7, 14, and 21 after PQ poisoning (all P＜0.05).After early LAS treatment, the apoptotic rate and Bax expression of lung decreased, the Bcl-2 expression increased, and the Bcl-2/Bax ratio increased, compared to the PQ group rats. Furthermore, the pathological results of lungs revealed that after LAS treatment, early manifestations of PQ poisoning, such as hemorrhage, edema and inflammatory-cell infiltration, were improved to some degree, and collagen fibers in the pulmonary interstitium were also obviously reduced.Conclusion In this rat model of PQ poisoning, LAS effectively ameliorated the lung injury induced by PQ, possibly through antioxidation, anti-fibrosis, anti-apoptosis, and anticoagulation.