Babies cry at night for the following common reasons: First, the difficult temperament, each person’s temperament is born different, can be divided into easy to raise type, difficult to raise type and intermediate type temperament. If the baby has a difficult temperament, it will be a big headache for the parent from a young age, and it will be a lot of work to bring the baby to the child growth and development department for temperament assessment. Second, vitamin D deficiency rickets, can be given vitamin D and calcium supplements will gradually be improved, can be clarified by trace element testing. Third, sleep-dependent behavior, this phenomenon is more common, after waking up at night must be given by parents to hold or rocking before gradually fall asleep, can be given gradually fading method, that is, when the baby wakes up without holding, only give words to comfort, gradually will be improved. Fourth, environmental factors, the ambient temperature is too high or too low, the baby’s clothing is too thick or too little, will lead to crying.