The so-called bone age criterion refers to the average age at which a specific X-ray skeletal image appears in the population, which is used as a benchmark to determine the bone age of each specific child. At present, there are three commonly used bone age criteria: (1) Standard atlas method: the bone age is determined according to the series of X-ray atlas of the wrist bones, one set for each sex, each X-ray represents an age standard bone age, and the bone age can be determined by comparing the unknown X-ray films with the atlas one by one and finding the atlas that is most similar to it. This method is simple and clear, and is commonly used in pediatric clinics. (2) Scoring method: According to the changes of morphology and size of each bone in the wrist during the maturation process, the bones are artificially divided into several stages, and the corresponding scores are given separately and then the corresponding bone age is converted after accumulating the total scores. This method is comprehensive and objective, with high accuracy. However, this method is cumbersome and requires special training to make effective judgments based on a good grasp of the different manifestations of each bone developmental stage. Therefore, it is not commonly used in general outpatient clinics. (3) Single index assessment method: Based on the appearance of several ossification centers or the age of epiphyseal healing in certain areas. Generally, the age group in which the emergence rate is located is the normal standard, and the age in which the emergence rate is 3% to 97% is the normal range. This method is simple, but the accuracy is poor, and there is a lack of organic connection between the indicators, which cannot reflect the development and maturity of the bones comprehensively. In conclusion, each method of determining bone age has its own advantages and disadvantages. Generally, the atlas method is suitable for the age below 7 years, and the scoring method is effective and accurate for determining bone age after 7 years, especially during puberty.