The baby cries when he goes to sleep at night, which may be caused by physiological factors, or indigestion, vitamin D deficiency and other reasons. 1. Physiological factors: if the baby sleeps too much during the day or is frightened during the day, the symptom of crying at night will occur. 2. Indigestion: due to the baby’s young age, the digestive system is not yet very perfect, if eaten before going to bed is not easy to digest the food, will increase the burden on the stomach and intestines, thus appearing to sleep at night to cry. 3. lack of vitamin D: the baby to sleep at night on the crying may also be the lack of vitamin D caused by the baby in addition to sleep at night in addition to crying, will be accompanied by excessive sweating, irritability, occipital baldness and other symptoms. The baby to sleep at night to cry, there may be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.