Oligodendrocytes are myelin-forming cells of the central nervous system (CNS). The processes extending from each oligodendrocyte are capable of wrapping axon to form multiple myelin sheaths to ensure efficient and rapid conduction of action potentials along the axon. Recent studies have shown that myelin changes are quite active although most of the myelin sheaths in the adult brain are in a stable state. On the one hand, oligodendrocyte precursor cells continue to differentiate to form new myelin sheaths; on the other hand, a small portion of the formed myelin sheaths degenerate over time. Dynamic changes in myelin sheaths are thought to be a form of neural plasticity in the adult brain, which aims to regulate the function of neural circuits for adapting of new environments or acquiring new skills. In the brains with Alzheimer's disease (AD), myelin degeneration can lead to a compensatory increase in myelin regeneration, but it is still insufficient to compensate for the loss of myelin, and the promotion of new myelin formation is expected to be a new strategy to improve AD-related cognitive dysfunction.