With the improvement of people’s living standard, more and more patients require orthodontic treatment. Most parents and children only notice the misalignment of teeth, but do not recognize the other aspects of orthodontic at the same time, especially for some bony misalignment can not be detected at an early stage, which often makes the child miss the optimal treatment time. Regarding the best age for orthodontic treatment, it depends on the type of teeth misalignment of the child, and is generally divided into three phases: I. Mastodontic phase (4-5 years old) This phase is mainly applicable to the antomandibularity of the milk teeth (pericoronation), and early orthodontic treatment is favorable to the development of the maxillary bone, and prevention of the antomandibularity of the permanent teeth. If the child has bad habits (such as tongue stretching, lip biting, etc.), it can also be corrected at this stage to prevent the occurrence of wrong jaw. Second, teething stage (girls: 8-10 years old, boys: 9-12 years old) Applicable to the early stage patients with functional and bony misalignment due to bad habits, tongue interference and other factors. During the teething stage, if you find that your child has bad habits (e.g. lip biting, tongue protrusion, protruding lower jaw, etc.), abnormal facial shape, and abnormal tooth arrangement, you should bring your child to the hospital to find an orthodontist for examination and consultation in order to determine whether it’s a dental, functional, or osseous malocclusion, and to determine the time of treatment and the treatment plan in this way. Because this stage is the pre-puberty and peak period of growth and development, if your child is functional or bony malocclusion, then treatment at this stage can make full use of the growth potential of the jaws, and achieve the therapeutic purpose by promoting or inhibiting the growth of the jaws, which is more beneficial to improving the child’s facial shape and function. Third, the stage of permanent teeth (girls: 11-14 years old, boys: 13-15 years old) Generally common malocclusion can be well treated at this stage. In addition, individual serious malocclusion, such as family history of “severe antomandibular”, should be treated with orthognathic surgery after the age of 18, in order to achieve ideal results.