Background　Neuroinflammation is implicated in the development of chronic neurodegenerative diseases in aging population, including postoperative cognitive dysfunction(POCD), Azheimer′s disease (AD), Parkinson′s disease(PD), and so on. The exact mechanisms, however, remain unclear.　Objective　To review the altered neuroinflammation and microglia activation in the aging brain.　Content　The activation of microglia appears in the aging brain, showing neuroinflammation, POCD, and neurodegeneration. The phenomenon is related to age-associated priming of microglia which increases its vulnerability and damages its function.　Trend　Suppressing microglia activation is one of the promising strategies to combat age-related neurodegenerative diseases.