Objective To examine the role of mitochondrial unfolded protein response（mtUPR） mediated by the protein kinase RNA-like ER kinase（PERK） signaling pathway in hypoxic-ischemic brain injury（HIBI）. Methods Rats were randomly divided into the sham group and five HIBI groups（3，6，12，24 and 48 h after HIBI） for Western blot analysis of PERK，activating transcription factor 4 （ATF4），and heat shock protein 60（HSP60） protein expression over time. In another experiment，rats were randomly divided into the sham group，HIBI group，HIBI+PERK group，and HIBI+Vector group，with 15 rats in each group. Rats in the HIBI+PERK group and HIBI+Vector group were given intracerebroventricular injection of adeno-associated virus（AAV）-based PERK overexpression plasmid or empty AAV vector 1 h before HIBI to induce specific PERK expression. FJC staining was performed 24 h after HIBI to analyze neuronal degeneration，and oxidative stress was examined by DHE staining and enzyme-linked immunosorbent assay. In a third experiment，rats were randomly divided into the sham group，HIBI group and HIBI+CCT020312（PERK agonist） group，with 12 rats in each group. Rats in the HIBI+CCT020312 group were given intracerebroventricular injection of CCT020312 one hour before HIBI. Open field test and Morris water maze test were performed 3 weeks after HIBI. Results Compared with the sham group，the HIBI groups showed significantly increased PERK，ATF4，and HSP60 expression at 3 h post-HIBI，which peaked at 12 h and then gradually decreased until 48 h（F=60.23，56.72，74.31，all P<0.001）. The HIBI+PERK group had significantly lower number of degenerated neurons（100.2±3.1 vs. 582.4±15.7，P<0.001），reactive oxygen species（ROS） level （42.4±2.9 vs. 17.7±2.1，P<0.01），and malondialdehyde（MDA） level（0.81±0.06 vs. 0.54±0.04，P<0.001），but significantly higher glutathione peroxidase（GSH-Px） activity （112.4±3.6 vs. 177.5±6.6，P<0.05） and superoxide dismutase （SOD） activity （46.3±1.9 vs. 64.2±2.3，P<0.05），as compared with the HIBI group. PERK（1.00±0.03 vs. 1.66±0.08，P<0.01），ATF4 （1.00±0.04 vs. 1.53±0.06，P<0.05），dynamin-related protein 1 （Drp1；1.00±0.02 vs. 1.98±0.07，P<0.01），and HSP60 （1.00±0.03 vs. 1.37±0.04，P<0.05） protein expression in the hippocampal tissue were significantly higher in the HIBI group than in the sham group. Furthermore，the HIBI+PERK group demonstrated significantly higher PERK（1.66±0.08 vs. 2.95±0.17，P<0.01），ATF4（1.53±0.06 vs. 3.42±0.22，P<0.01），and HSP60 （1.37±0.04 vs. 2.03±0.09，P<0.05） protein expression（F=46.72，30.63，20.64，P<0.001） but significantly lower Drp1（1.98±0.07 vs. 1.04±0.05，P<0.05） protein expression in the hippocampal tissue than the HIBI group（F=35.72，P<0.001）. Mean escape latency and the number of platform crossings were significantly higher in the HIBI+CCT020312 group than in the HIBI group（F=246.84，113.62，P<0.001）. Conclusion PERK attenuates oxidative stress and neuronal apoptosis induced by HIBI，possibly through the regulation of mtUPR via the PERK/ATF4 signaling pathway. CCT020312 has neuroprotective effects in HIBI.