To investigate the effects of hypoxia-reoxygenation (H/R) on hippocampal neurons and endoplasmic reticulum stress in mice. HT22 hippocampal neurons were used for subsequent experiments after H/R treatment. CCK8 and scratch test were used to detect the proliferation and migration of HT22 hippocampal neurons to observe the effect of H/R on HT22 hippocampal neurons. The effect of H/R on the morphology of endoplasmic reticulum was observed by transmission electron microscopy, and the effect of H/R on the development of HT22 hippocampal neurons was observed by immunofluorescence. Western-Blot and qRT-PCR were used to observe the effect of H/R on endoplasmic reticulum stress in hippocampal neurons. The results showed that compared with the control group, H/R inhibited the proliferation and migration of HT22 hippocampal neurons, and the expression of neurodevelopmental protein BDNF was decreased. In addition, H/R also reduced the expression of synaptic plasticity proteins PSD-95 and α-Syn. The effect of H/R on ER stress is reflected in the swelling of ER caused by H/R, which promotes the expression of ER stress signals such as GRP94, BIP and ATF6. Therefore, H/R has a damaging effect on HT22 hippocampal neurons, which may be related to enhanced ER stress.