Human milk oligosaccharides are abundant and unique in human milk， 200 components have been detected， of which 157 structures have been identified. HMOs not only has the effect of ‘bifid factor’， but also has anti adhesion， anti-bacterial， regulating intestinal epithelium and immune cells， reducing excessive mucosal leukocyte infiltration and activation， reducing neonatal necrotizing enterocolitis， and providing sialic acid as a potential essential nutrient for brain development and cognition for infants. Chemical and biosynthetic HMOs substitutes are constantly emerging due to limitations on large-scale production. Although classic substitutes such as galactooligosaccharides and fructooligosaccharides have some part of the functions of HMOs， their structural composition is significantly different. 2'-Fucosyllactose and lacto-N-neotetraose only simulate one or several molecular structures in HMOs. Therefore， bovine oligosaccharide has obvious advantages. Based on the review of the content， classification， structural characteristics， analysis methods， physiological functions， digestion， absorption and synthesis of milk oligosaccharides in different lactation stages， this paper focused on the potential sources of milk oligosaccharides. It aimed to provide theoretical guidance for the research， development and industrial substitution of HMOs substitutes.