Hydrogen sulfide (H₂S) is an endogenously generated gaseous mediator and can regulate a series of physiological and pathological processes of mammals. In recent years, the physiological and pathological effects of H₂S on the central nervous system attract more and more attention. H₂S can promote the longterm potentiation of hippocampus and regulate the intracellular calcium concentration and pH level of brain cells as a neuromodulator. H₂S can also protect the nervous system from oxidative stress, apoptosis, or degeneration. Dysregulation of H₂S is implicated in the pathological processes of Alzheimer's disease (AD). This paper reviews the potential mechanism of protective role of H₂S in AD.