The optimal age for orthodontic treatment varies from one malocclusion to another. During the period of teething (3 to 5 years old) and the period of tooth replacement (6 to 11 years old), general malocclusions such as individual teeth misalignment and physiological temporary misalignment do not require immediate orthodontic treatment and should be followed up to observe and correct bad oral habits. Because in this period, the teeth and jaws are in the adjustment stage, with the removal of bad habits, malocclusion can often correct itself. Growth and development is rapid at this time, and inappropriate orthodontic forces can affect development. However, for deformities that affect the growth and development of the oral and jaw systems, impede oral function and endanger health, timely orthodontic treatment is required. For example, if the milk teeth are reversed, the growth of the upper jaw is inhibited by the obstruction of the lower front teeth, and the growth of the lower jaw is overgrown by the thrust of the upper jaw growth. This forms a vicious circle, making the deformity more and more severe with age. Therefore, it should be treated early. Most malocclusions are not treated until the permanent period when teeth are replaced, about 12 to 14 years old. Because the permanent tooth roots are gradually developed and the occlusal relationship between the upper and lower teeth is adjusted, a clear diagnosis of the type of malocclusion can be made and the corresponding orthodontic treatment can be adopted. The orthodontic treatment is easy to maintain a stable effect after completion and will not change significantly. Theoretically, the best age for orthodontic treatment of malocclusion in children is during the growth spurt of children. Boys are between 12 and 14 years old and girls are between 11 and 13 years old. However, there are individual differences in the growth and development of each child, and no generalizations can be made. The correct way to estimate the growth spurt is through certain tests. Such as taking wrist X-rays, continuous height measurements, knowing the first menstrual period of women, and paying attention to children’s shoes, socks, clothing and hats. Correction during this period is a short course of treatment and effective. If you miss this period, such as 15 to 17 years old, still in the adolescent period, growth and development is still relatively active, although the difficulty increases slightly, but the orthodontic effect is also better. However, for severe bony malocclusion, the orthodontic treatment cannot be completed by orthodontic methods alone and must wait until the adult period after the age of 18 with orthognathic surgery for treatment.