In the clinic, some parents often think that orthodontic treatment can only be done after the teeth have been replaced, but this view is one-sided. Different malocclusion has different timing of correction, so it should be determined according to the specific circumstances of the malocclusion, and can not be completed at the age of 12 years old after tooth replacement. Generally speaking, patients with simple malocclusion and minor facial bone deformities should start orthodontic treatment after teeth replacement, generally 12-14 years old for boys and 11-13 years old for girls. At this time, the body is in the period of rapid development of youth, the degree and complexity of malocclusion has been fully realized, which is conducive to the doctor’s diagnosis and orthodontic design; at the same time, this stage of rapid growth, orthodontic treatment has a good response, it is easier to achieve good therapeutic results. However, some cases that may develop into serious facial skeletal deformities should be treated early. For example, bony anastomoses should be treated at about 4 years of age.