Objective: To investigate the effect of GdCl3 pretreatment on the tumor suppressor CYLD and NF-κB in alveolar macrophages (AMs) of rats with acute lung injury induced by acute necrotizing pancreatitis (ANP), so as to explore the role of CYLD in acute lung injury secondary to ANP. Methods: Thirty-six SD rats were equally randomized into the normal control group, ANP group and GdCl3 pretreatment group. The ANP model was established by retrograde injection of 5% sodium taurocholate into the biliopancreatic duct and the GdCl3 pretreatment group were injected with GdCl3 (10 mg/kg) through tail vein 30 min prior to model establishment. Animals were sacrificed 6 h after ANP induction, and then the AMs were harvested via bronchoalveolar lavage. The contents of TNF-α and IL-1β in bronchoalveolar lavage fluid (BALF) were detected, and the activation levels of NF-κB and CYLD in AMs were determined by Western blot analysis. The myeloperoxidase (MPO) activity levels in the lung tissues were measured and pathological examination of the lung tissues was performed. Results: No pathological change was found in lung tissues of the normal control group, while the lung tissues of both the ANP and GdCl3 pretreatment group showed marked pathological changes such as congestion, edema and accumulation of inflammatory exudates, but these changes of the GdCl3 pretreatment group were relatively mild compared with the ANP group. The MPO activity level in the lung tissues, and the contents of TNF-α and IL-1β in the BALF were all significantly increased in the ANP group compared with the normal control group (all P<0.05). The relative expression levels of NF-κB in the normal control group, ANP group and GdCl3 pretreatment group were 0.08±0.03, 0.18±0.06 and 0.11±0.04, and the relative expression levels of CYLD of the three groups were 0.32±0.09, 0.15±0.05 and 0.27±0.07, respectively. There were negative correlations between the expression of NF-κB and CYLD in the AMs of the ANP group and GdCl3 pretreatment group (r=–0.708 and r=–0.571, both P<0.05). Conclusion: There is reduced CYLD expression and activated NF-κB expression in the impaired lung tissue associated with ANP. GdCl3 can up-regulate the CYLD expression and inhibit the NF-κB activation, thereby ameliorate the lung injury secondary to ANP.