Human milk oligosaccharides (HMOs) are complex carbohydrates with unique structures in human milk， and their diversity is much higher than that of other mammalian milk. The functional role of HMOs can continue from the initial establishment of infant gut microbiota to adulthood， including supporting beneficial bacterial growth and anti-pathogen adhesion. It also has the potential to produce beneficial effects in cognition. It is worth further studying whether HMOs can promote the healthy development of the infant brain by regulating the intestinal flora and using the gut-brain axis. This paper reviewed the composition and structure of HMOs， focused on the role of HMOs in shaping the intestinal flora of infants， and discussed the promotion of HMOs and their metabolites on infant cognition through the gut-brain axis， aiming to provide a theoretical reference for promoting the application of HMOs in infant formula.