As a normal physiological substance, D-galactose can induce a process similar to natural brain aging in vivo and in vitro when administered excessively, and thus it is widely used to induce brain aging models in China and abroad. The model of brain failure induced by D-galactose has the advantages of a short modeling time, low cost, and significant effect. However, the induction mechanisms are complex and diverse, and the relationships between the mechanisms are unclear, which limit the practical applications of the model. This article reviews the in vivo metabolism of D-galactose and the various mechanisms involved in the induction of brain aging, as well as the links between the mechanisms, to provide a reference for the application and development of this model and the in-depth study of brain aging.