The common reasons for children crying at night include environmental discomfort, gastrointestinal disorders, and nutrient deficiencies. 1. Environmental discomfort: such as the outside environment temperature is too high, too low, more noisy, turn on the light to sleep, wrapped too tightly or overdressed, sleep will cause the child to feel uncomfortable, caused by night crying. 2. Gastrointestinal dysfunction: If you eat and drink more before going to bed, you may experience nausea, vomiting, indigestion, abdominal pain and other symptoms, and your child may cry at night. 3. Nutrient deficiency: Vitamin D deficiency can lead to increased neural excitability of the baby, night crying, excessive sweating, easy to startle and other manifestations, and rickets can occur in severe cases. Children crying at night may also have other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.