Sialic acid is an acidic monosaccharide with a 9-carbon skeleton， which is usually located at the end of non reducing oligosaccharides. Human milk is rich in sialic acid， which plays an important role in promoting the brain and cognitive development of infants and young children， antivirus and other aspects. At present， sialic acid is mainly prepared by microbial fermentation in industry. This paper analyzed the principle， method and prospect of sialic acid in infant food from the aspects of its properties， distribution， function and preparation methods， so as to provide theoretical support for improving the application of sialic acid in maternal and infant food.