The cause of the soft skull of newborns is mainly due to the following two conditions. First, it is the reason that the newborn belongs to the preterm baby, if the newborn belongs to the obvious preterm birth, the development of each organ is not too mature, unlike the full-term baby complete and hard, the newborn will appear to have a soft skull. Close care is required, and in most cases the newborn skull will improve significantly with age. Secondly, it is caused by neonatal vitamin D deficiency rickets, if the newborn has a blood vitamin D as well as blood calcium significantly low, the calcification of the newborn’s bones will be affected, thus causing the newborn’s skull soft. Parents should give newborns vitamin D as well as calcium supplements in time.