DNA methylation is one of the main modification modes in epigenetics. 5-hydroxymethylcytosine （5hmC）， as a product of DNA demethylation， has become a new epigenetic marker. Due to the high distribution of 5hmC in the central nervous system and the constant changes in the process of neurodevelopment， it is very important for normal neurodevelopment and neurological function. Recent studies have found that 5hmC imbalance caused by aging or environmental stress may play an important role in the occurrence and development of diseases. Therefore， this article reviews the role of 5hmC in neurodevelopment and neurodegenerative diseases in recent years.