The present study investigates the ameliorating effects of emodin on acute lung injury (ALI) induced by severe acute pancreatitis (SAP). An ALI rat model was constructed by sodium ursodeoxycholate and they were divided into four groups: SHAM, ALI, emodin and dexamethasone (DEX) (n=24 per group). Blood samples and lung tissues were collected 6, 12 and 24 hours after the induction of SAP‐associated ALI. Lung wet/dry ratio, blood gases, serum amylase and tumor necrosis factor‐α (TNF‐α) were measured at each time point. The expressions of AQP1 and AQP5 in lung tissue were detected by immunohistochemical staining, western blotting and real‐time PCR. As the results show, there were no statistical differences in the levels of serum amylase, lung wet/dry ratio, blood gases indexes, serum TNF‐α and pathological changes between emodin and DEX groups. However, significant differences were observed when compared with the ALI group. AQP1 and AQP5 expressions were significantly increased and lung oedemas were alleviated with the treatment of emodin and DEX. The expressions of AQP1 and AQP5 were significantly decreased in SAP‐associated ALI rats. Emodin up‐regulated the expression of AQP1 and AQP5, it could reduce pulmonary oedema and ameliorate SAP‐induced ALI. Regulations on AQP1 and AQP5 expression had a great value in clinical application.