Calcium is an important component of human bones. The normal growth and development of bone tissue requires the intake of the right amount of calcium. For infants and young children, the daily intake of the right amount of calcium can promote growth and development, and a healthy, safe and scientific calcium supplement is especially important. The balance of calcium in infancy depends mainly on the nutrition of calcium and vitamin D. The main cause of calcium deficiency in infants and young children is insufficient intake of vitamin D (VD), and lack of vitamin D can affect the absorption of calcium and lead to rickets. At the beginning, there are signs of sleep disturbance, excessive sweating, crying at night, and irritability, and at a later stage, there are skeletal changes such as enlarged fontanelle, delayed closure, softening of the skull, occipital baldness, chicken chest, funnel chest, rib cage exostosis, and O- or X-shaped legs. The World Health Organization recommends exclusive breastfeeding for babies under 6 months of age. Breast milk is rich in nutrients, a natural food for babies, and very high in calcium. The daily calcium requirement for newborns is about 300mg, and the calcium in breast milk can fully meet the daily physiological requirement of babies, so there is no need for additional calcium supplements. Babies who do not have enough breast milk or cannot be breastfed need to add infant formula, and qualified infant formula also contains the right amount of calcium, and there is no need to supplement calcium, but they need to supplement vitamin D to promote calcium absorption and prevent vitamin D deficiency rickets. The amount of vitamin D brought by the mother can only maintain the baby’s needs for 2 weeks, and the amount of vitamin D in breast milk is very low, so it should be supplemented from half a month after birth, 400 IU per day. after 1 year old, the requirement of vitamin D reaches 600 IU per day, but as the baby’s outdoor activities increase, the doctor needs to evaluate the baby’s diet and activities to determine the dose of vitamin D to be taken. Low weight babies (<2.5 kg at birth), premature babies (<37 weeks), twins, these babies get less vitamin D from the mother but grow more rapidly, so the vitamin D supplementation is 800 IU per day, and after 3 months it can be changed to 400 IU per day like normal babies. Calcium is essential for growth and development, but blindly supplementing calcium will inevitably affect the absorption of other Calcium is essential for growth and development, but blindly supplementing calcium will affect the absorption of other trace elements, so it is necessary to supplement calcium scientifically and appropriately.