The main role of probiotics is to protect infants’ intestinal tract, inhibit harmful bacteria and toxins in the intestinal tract; activate the activity of infants’ immune system to improve infants’ resistance; provide essential nutrients to promote human growth and development. Clinical studies have shown that the microecology of the human intestinal tract is gradually established from birth, and after the age of 2 is the golden period for the gradual improvement of the gastrointestinal microecology. However, the establishment of human gastrointestinal microecology is influenced by many factors, including the mode of birth, whether born at full term or not, and the way of breastfeeding. For example, newborns born by normal birth have a higher number of normal colonized bacteria in their intestines than those born by cesarean section, and the flora is more stable. At the same time, full-term newborns have a more stable and mature microecology than preterm infants, and their immune system is also established earlier. Therefore, babies born by cesarean section, premature babies and formula-fed babies all need probiotic supplementation in time. In addition, when infants are sick, the micro-ecological balance in the gastrointestinal tract will be affected, and they also need to be supplemented with sufficient amount of probiotics in time to maintain the micro-ecological balance in the infant’s intestinal tract.