The injury of exogenous formaldehyde and its merchanism have attracted wide attention from researchers. The latest study found that mammals have a whole system for generating and clearning formaldehyde. However, the imbalance on the system for generating and clearning formaldehyde for various reasons will cause abnormal accumulation of endogenous formaldehyde in vivo, which is closely related to learning diability and memory dysfunction. The increase in endogenous formaldehyde concentration may be one of factors inducing such neurodegenerative diseases as Alzheimer's disease. The study on the relationship between endogenous formaldehyde and such neurodegenerative diseases as Alzheimer's disease is of great significance and can provide new thoughts for preventing and treating Alzheimer's disease with traditional Chinese medicines.