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), which can affect calcium absorption and lead to rickets. In the early stage, there are signs of sleep disturbance, excessive sweating, crying at night, and irritability. Later on, there are skeletal changes such as enlarged fontanelle, delayed closure, softening of the skull, occipital baldness, chicken chest, funnel chest, rib exostosis, and O- or X-shaped legs. Since babies within 2 years of age have little outdoor exercise, it is recommended to supplement VD daily. For babies aged 0-6 months, if they are exclusively breastfed or fed with qualified infant formula, the calcium in breast milk or formula can meet their daily physiological requirements and no additional calcium supplements are needed, but vitamin D supplementation is needed to promote calcium absorption and prevent vitamin D deficiency rickets. Vitamin D can be supplemented half a month after birth and is recommended until the age of 2. However, for premature babies and low birth weight babies, they need higher calcium intake, so they need additional calcium supplementation. children over 6 months of age have a reasonable diet, pay attention to food supplementation of calcium, and in general only VD supplementation is sufficient. If the child is really deficient in calcium, or suffers from certain diseases, he or she can take calcium supplements and choose the right one according to the severity of the calcium deficiency. Calcium is essential for growth and development, but blindly supplementing calcium will inevitably affect the absorption of other trace elements, so a scientific and appropriate amount of calcium supplements is needed. Calcium vitamin D supplementation is the key.