Microglia are very important immune cells, which are widely distributed in the central nervous system. They continuously monitor and sense the surrounding microenvironment, balancing the body's immune response by releasing various cellular inflammatory factors on the one hand, and regulating neural network function through phagocytosis of synapses and cells on the other. Dysfunction of microglia is a primary mechanism involved in the onset or exacerbation of neurodegenerative diseases, thus restoring microglial function may represent a potential therapeutic modality. CD22, an important member of the sialic acid-binding immunoglobulin-like lectin family, is typically expressed on the surface of B cells and serves an immunoinhibitory role. Recently, CD22 has been shown to improve cognitive function in aged mice through microglia, a discovery that holds promise for CD22 to become a novel target in the treatment of neurodegenerative diseases.