Bone age refers to the actual age at which the human skeleton develops, and a normal bone age means that the human skeleton is in a normal state of development. Smaller bone age indicates delayed bone development, which may be caused by metabolic diseases or insufficient nutritional intake, such as the decline of pituitary function, thyroid and gonadal insufficiency, or juvenile diabetes can lead to delayed bone development, that is to say, the state of small bone age. Commonly, nutritional deficiencies, mainly vitamin D and calcium deficiencies, lead to delayed bone age. In this case, we should check the calcium and vitamin D levels in the blood in a timely manner, and then replenish the relevant nutrients in a timely manner, so as to correct the state of small bone age in a timely manner.