Babies crying, especially at night, is a headache for parents and they don’t know what to do. So when faced with a crying baby, we should understand what the cause of the crying is? Then it will be easy to solve the right problem. 1, may be caused by vitamin D deficiency, whether exclusive breastfeeding or formula feeding can not meet the needs of infants vitamin D, vitamin D deficiency, will cause disorders of calcium and phosphorus metabolism. Early on, there will be irritable, irritable, easily startled and other symptoms of increased excitability of the nervous system. Vitamin D deficiency is a preventable and treatable disease. Regular oral intake of vitamin D and appropriate increase in outdoor activities can ensure the body’s demand for vitamin D and improve the symptoms of increased neurological excitability in infants. Parents should create a familiar environment for the infant as much as possible, to help the infant become familiar with and accept the surroundings, and not to change the primary janitor too often. In this case, parents need to have patience to reassure the infant and not to be impatient. 3, the baby’s digestive system is not yet mature, too much air inhalation caused by the milk too quickly, coupled with continuous crying makes the flatulence aggravated. It is necessary to hold the baby upright, pat the back, keep the tummy warm and slowly let the baby expel the gas.