Objective To study the effect of dual GIP/GLP-1 receptor agonist DA5-CH on cerebral ischemia-reperfusion (I/R) injury in rats and the potential underlying mechanisms.Methods Thirty cerebral I/R injury rat models were randomly divided into model group, DA5-CH group, and DA5-CH + SB431542 group, with 10 rats in each group. Another 10 rats only underwent sham operation and were set as sham group. Rats in the DA5-CH group were intraperitoneally injected with DA5-CH at a dose of 10 nmol/kg, those in the DA5-CH + SB431542 group were intraperitoneally injected with DA5-CH at a dose of 10 nmol/kg and SB431542 at a dose of 5 mg/kg, while those in the sham group and model group were intraperitoneally injected with an equal volume of normal saline. The water content of the brain tissues of rats was detected. The number of neuronal nuclear antigen (NeuN)-positive cells in hippocampal CA1 area was determined by immunohistochemical staining. The protein expressions of transforming growth factor β₁ (TGF-β₁), Smad3, and p-Smad3 in brain tissues were detected by Western blotting.Results Compared with the sham group, the water content of brain tissues was increased, the number of NeuN-positive cells in each field of hippocampal CA1 area was decreased, and the protein expressions of TGF-β₁ and p-Smad3/Smad3 in brain tissues were increased in the model group (P < 0.05). Compared with the model group, the water content of brain tissues was decreased, the number of NeuN-positive cells in each field of hippocampal CA1 area was increased, and the protein expressions of TGF-β₁ and p-Smad3/Smad3 in brain tissues were decreased in the DA5-CH group (P < 0.05). Compared with DA5-CH group, the water content of brain tissues was increased, the number of NeuN-positive cells in each field of hippocampal CA1 region was decreased, and the protein expressions of TGF-β₁ and p-Smad3/Smad3 in brain tissues were increased in the DA5-CH + SB431542 group (P < 0.05).Conclusions The dual GIP/ GLP-1 receptor agonist DA5-CH can protect the neurological function of rats with cerebral I/R injury, reduce the brain water content, and ameliorate the neuronal necrosis and pathological changes in the hippocampus. The underlying mechanism may be related to the activation of TGF-β₁/ Smads pathway.