Abstract: Bifidobacterium longum is an important probiotic in human and animal intestines, which is related to many physiological and pathological phenomena of the body cloesly. Its prebiotic function in relieving metabolic syndrome, brain gut syndrome and immune related diseases has become a hot spot of experts in various fields. In order to deepen and improve the understanding of Bifidobacterium longum, this paper reviews the biological characteristics of subspecies identification and colonization of Bifidobacterium longum, the hot prebiotic function in relieving metabolic syndrome, brain gut syndrome and immune syndrome, as well as the research progress and hot application prospect at home and abroad.