When we talk about calcium deficiency in babies, we are actually referring to vitamin D deficiency in babies, because vitamin D promotes calcium absorption, and insufficient intake of vitamin D will affect calcium absorption, thus showing calcium deficiency. Calcium deficiency in babies mainly affects muscle development and also shows changes in neuroexcitability. In early infants, especially those within 3-6 months of age, neuroexcitability is increased, such as irritability, head sweating, head shaking, and occipital baldness. When this stage is not treated aggressively and the condition continues to worsen, the typical skeletal changes of calcium and phosphorus metabolism malfunction can occur. The child may develop cranial softening, late closure of fontanelle, square skull after 6 months of age, rib crosstalk, especially in the 7th to 10th ribs, chicken chest, shaking chest, Hao’s sulcus, and other skeletal deformities. In particularly severe cases, backbending or scoliosis of the spine and deformities of the pelvis may also appear. The limbs may have bracelets, ankle bracelets, O-leg, X-leg, etc. In particularly severe cases, the child may have low muscle tone and strength, along with malnutrition and anemia, and in some cases, enlargement of the liver and spleen. When a child shows the above symptoms, we should consider that the child is suffering from calcium deficiency caused by vitamin D deficiency, so we should routinely test the level of vitamin D in the blood, check the level of blood calcium, blood phosphorus, alkaline phosphatase, and take skeletal X-rays, and once the diagnosis is confirmed, we should actively treat the child as soon as possible.