Breastmilk is the juice produced by a woman’s breasts after giving birth and is used to nurse her baby. Breastmilk is white, alkaline, with a specific gravity of 1.030 and a daily volume of 700 to 1,000 ml. It is secreted by the breasts of postpartum women, and is a natural and irreplaceable food for infants, which can satisfy their growth and development. Breastmilk is rich in nutrients and contains the right proportion of essential amino acids, β-casein, whey protein, lactose B, more unsaturated fatty acids, small protein molecules, low electrolyte concentration, which are easy to be digested and absorbed by infants and promote the development of the body and brain, and promote the production of B vitamins. In addition, breast milk is rich in SIgA, a large number of immunologically active cells, lactoferrin and other substances, all of which are irreplaceable sources of immune components for infants.