Ketamine is a noncompetitive N‑methyl‑D‑aspartate (NMDA) receptor antagonist, which has been used as a dissociative anesthetic. In recent years, It has been shown that ketamine may have neuroprotective effect, which can improve cognitive function. This article reviews the relevant literature and discusses the research progress of ketamine's neuroprotective effect in preventing perioperative neurocognitive disorder (PND) and improving the cognitive function of patients with major depressive disorder, patients with acute neurologic injury and patients with Alzheimer's disease as well as the possible mechanism.