Sudden crying at night is related to environmental factors, dietary factors, calcium deficiency and other factors. 1. Environmental factors, if the baby is often in a too noisy environment or the environment temperature is relatively high, it may affect the baby’s sleep, so the symptoms of sudden crying at night will occur. 2. Dietary factors, if the baby is hungry at night or if the baby is given too much food before going to bed at night, it may lead to the baby’s abdominal discomfort and this symptom. 3. Calcium deficiency, if calcium deficiency may lead to increased excitability of the nervous system in the body, skin sensation abnormalities, so it is more likely to appear in the baby suddenly crying at night symptoms. Babies suddenly cry at night, there may also be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to determine the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.