Babies always cry at night, the causes include physiological and pathological, pathological babies cry at night due to calcium deficiency, intussusception and other reasons. 1. Physiological reasons: babies cry all the time at night may be normal physiological needs, such as hunger or the need to defecate, etc. It may also be due to the indoor temperature is too high, the environment is too noisy, etc., affecting the baby’s sleep, which can also lead to frequent crying at night. 2. Calcium deficiency in infants and young children: due to the rapid development of babies, such as failure to add complementary foods in a timely manner or insufficient exposure to sunlight, etc., can lead to a lack of vitamin D in the body, or cause calcium and phosphorus metabolism disorders and thus the symptoms of calcium deficiency. Children may cry at night, accompanied by irritability, night sweating, yellow hair and other symptoms. 3. Intussusception: It occurs mostly in children and may be caused by the disturbance of peristaltic rhythm of the intestines. Children with intussusception may have sudden severe regular paroxysmal colic, which may be manifested by crying and restlessness, pallor, vomiting, bloody stools and so on. Babies cry all the time at night, after excluding physiological causes, should promptly consult a doctor to clarify the cause of the disease, and if necessary, appropriate treatment.