Abstract: According to clinical epidemiological researches, the usage of antibiotics in infant increases the risk of childhood asthma morbidity. The mechanism of this link is not entirely clarified, and it is assumed of being related to side effects of antibiotics, which changes the colonization of normal intestinal flora and reduces the diversity. It is clear that normal intestinal flora of infant help to construct innate immune system and adaptive immune system, and forge immune tolerance. Therefore, normal intestinal flora might be helpful in reducing allergies. The usage of antibiotics in early life changes the quantity and the composition of intestinal flora, and breaks the balance of immune homeostasis, which might increase the risk of asthma morbidity. The abuse of antibiotics in children is a general phenomenon in China which needs attention from pediatricians.