Abstract: Bifidobacterium BB-12 belongs to the 12th strain of Bifidobacterium animalis subsp.lactis BB-12, commonly used in infant formula powder, food additives and yogurt, and is the most documented Bifidobacterium.In this review, we describe the effect of BB-12 on gut microbiota, and investigate the effects of BB-12 on regulating immune function, reducing infection and improving resistance in infants, children and adults.