Objective To explore the protective effects and mechanisms of cysteinyl leukotriene 2 (CysLT₂) receptor antagonist HAMI3379 on cerebral ischemia injury in rats. Methods 30 male SD rats were randomly divided into sham operation group, model group, and HAMI3379 group, with 10 rats in each group. The rats of model group were subjected to middle cerebral artery occlusion (MCAO) to construct the cerebral ischemia injury model, while HAMI3379 group received intraperitoneal injection of HAMI3379 (0.2 mg/kg) before and after MCAO 30 min. The rats after cerebral ischemia injury were scored for neurological symptoms. The infarction volume of rats was observed by TTC staining, the activation marker Iba1 of microglia was detected by immunofluorescence staining, the mRNA level of M1/M2 polarized phenotype molecules of microglia was detected by Real-time PCR, the number of neurons was observed by NeuN staining, and neuronal degeneration was observed by Fluoro-Jade B staining. Western blotting assay was used to detect the expression of CysLT₂ protein and nuclear factors κB-related protein Cα (PKCα), IκBα, p65 and p50 proteins in brain tissue. Results Compared with sham operation group, the neurological symptom score and cerebral infarction volume of model group were significantly increased (P<0.05). Compared with model group, the neurological symptom score and cerebral infarction volume of HAMI3379 group were significantly decreased (P<0.05). The results of immunofluorescence staining showed that the expression of microglia activation marker Iba1 was increased in brain tissue of rats after cerebral ischemia injury (P<0.05). Compared with sham operation group, mRNA expression of M1 polarized molecules (CD86, IL-1β, TNF-α) and M2 polarized molecules (CD206, TGF-β, IL-10) were significantly increased in the ischemic central brain tissue of model group (P<0.05). Compared with model group, the expression of M1 polarized molecules in HAMI3379 group was significantly downregulated (P<0.05), while the expression of M2 polarized molecules was significantly upregulated (P<0.05). Compared with sham operation group, the expressions of PKCα, IκBα, p65 and p50 in brain tissue of model group were significantly up-regulated (P<0.05); compared with model group, the expressions of PKCα, IκBα, p65, and p50 in HAMI3379 group were significantly down-regulated (P<0.05). The NeuN staining results showed that the number of neurons in the brain tissue of model group was decreased when compared with sham operation group (P<0.05), while the number of degenerated neurons was increased (P<0.05). Compared with model group, the number of neurons in HAMI3379 group was increased (P<0.05), while the number of degenerated neurons was decreased (P<0.05). Conclusions CysLT₂ receptor antagonist HAMI3379 may regulate PKCα/IκBα/NF-κB signaling pathway, inhibits M1 polarization activation of microglia and promotes its transition to M2 polarization, inhibits neuronal degeneration, and plays a neuroprotective role.