Immune factors are always present in breastmilk, but after six months the nutrition of breastmilk usually decreases and the immune factors may become less. The immune factor in breast milk has an anti-infective effect. Within six months after birth, the baby’s immune system is still immature, and the immune factor in breast milk can protect the baby and enhance the baby’s resistance to germs and viruses, thus reducing the occurrence of diseases, so it is recommended that after giving birth to a child it is best to choose breastfeeding to be able to improve the baby’s immunity. But with the passage of time, the immune factor in breast milk will gradually decrease, the baby in six months should be added to the complementary food, at this time the baby’s gastrointestinal tract digestive function is gradually developed and perfect, can be appropriate to gradually increase the complementary food, in order to meet the baby’s body on the demand for nutrition.