Three-year-old children are very crying, may be caused by psychological factors, may also be caused by disease factors (vitamin D deficiency, indigestion, etc.). 1. Psychological factors: It is considered that the three-year-old child is not good at expressing himself and hopes to get the attention of his parents by crying, so that he can get more companionship and a greater sense of security. 2. Disease factors: (1) For example, when a child is deficient in vitamin D, he or she will show that he or she sleeps uneasily at night, cries easily, sweats more, has occipital baldness, and even develops poorly in terms of bones. (2) In addition, the consideration of pediatric indigestion, mainly manifested as epigastric pain, abdominal distension, early satiety, acid reflux, belching (hiccup), nausea, vomiting, anorexia, heartburn, etc., when more than three years old children with intestinal discomfort may be manifested in the form of crying. However, other factors can not be ruled out, it is recommended that parents who exclude physiological causes, should take their children to the doctor in a timely manner, please ask the doctor to clarify the cause of the disease, to give targeted treatment.