The main role of lactase is to promote digestion and absorption in the infant’s gastrointestinal tract. Lactase is an enzymogenic substance found mainly in breast milk, which can play an important role in promoting digestion in the infant’s digestive system and avoiding diarrhea and bloating. It can be used clinically to prevent constipation and diarrhea, to increase the level of nutrients in the body, and to benefit the body as a nutritional product. Lactase can be broken down into various monosaccharide substances in the body and plays an important role in the development of bone and brain of infants. Lactase can promote brain development and maintain the basal metabolism of infants. By supplementing breast milk in a timely manner during infancy, lactase can be supplemented for infants to prevent constipation and diarrhea and promote growth and development.