Vitamin D deficiency rickets is a chronic nutritional deficiency disease due to vitamin D deficiency and abnormal calcium and phosphorus metabolism in the body, resulting in skeletal lesions, and is one of the four major diseases in pediatrics in China. The clinical symptoms are mainly psychoneurological with some special signs, i.e. the child has non-specific neurological and psychiatric symptoms such as nocturnal cry, irritation, sweating, etc., which may be accompanied or partially accompanied by signs such as delayed sprouting, cranial softening, square skull, rib crosstalk, cockscomb chest, funnel chest, occipital baldness, enlarged fontanelle, rib ectropion, etc. Vitamin D deficiency rickets can occur at any time from the second week of life. Vitamin D maintains and regulates plasma calcium and phosphorus levels through its action on three target organs: the small intestine, kidney and bone. Vitamin D deficiency, mainly 1,25-(OH)2D3 deficiency, decreases the absorption of calcium and phosphorus from the intestine, leading to a decrease in blood calcium and phosphorus, prompting an increase in parathyroid hormone secretion and bone decalcification to maintain normal blood calcium, while prompting a decrease in phosphorus reabsorption by the renal tubules and an increase in urinary phosphorus and a decrease in blood phosphorus. Therefore, when vitamin D deficiency, blood calcium is at normal or low level, while blood phosphorus is reduced, so that the calcium and phosphorus concentration product (normal at 34-40) is reduced, calcium and phosphorus cannot be fully deposited in the bone matrix, and a large amount of bone-like tissue accumulates, resulting in rickets or osteochondrosis. Calcium is widely present in milk and food and is not easily deficient. The main cause of calcium deficiency in bone is vitamin D deficiency; therefore, clinically, 95% of rickets are caused by vitamin D deficiency. In addition to more sunshine outdoors, attention should be paid to vitamin D supplementation from 2 weeks after birth, especially for premature babies, who have the possibility of rickets one week after birth and should pay more attention to it.