The production of breast milk is the result of the combined action of lactogen and the lactation reflex. After the delivery of the fetus, the secretion of estrogen and luteinizing hormone in the pregnant woman’s body suddenly decreases, and the prolactin secreted by the anterior pituitary gland increases in large amounts. Prolactin acts on the lactating cells of the mammary gland, causing the enzymes related to lactogenesis to be activated by phosphorylation, promoting the synthesis of milk proteins, lactose and triglycerides, thus producing milk. Under normal circumstances, milk production starts 2-3 days after delivery as colostrum, 4 days to 2 weeks after delivery as transitional milk, and 14 days after delivery as mature milk. Milk is a white or slightly yellowish liquid, opaque and rich in nutrients, such as fat, protein, sugar and inorganic salts in various proportions. Breast milk is the natural food for infants, and it contains a large amount of immune substances that can greatly reduce the morbidity of infants. Its nutritional composition is fully adapted to the needs of infants from 4 to 6 months, so it is important to insist on breastfeeding for infants from 4 to 6 months. At 6 months of age, infants can add complementary foods. At this time, breastfeeding may affect the healthy development of infants and cannot meet their growth and development needs, so it is recommended to gradually reduce the amount of breast milk and gradually wean them from 10 months. If the infant’s resistance is poor, the weaning period can be extended to about 1 year old.