1, before the age of 6, all the teeth in the mouth are milk teeth. (1) The main malocclusion that should attract parents’ attention during the period of milk teeth is the anterior antipodal malocclusion, which is commonly known as “pericoronary” and “pocket teeth”, and should be corrected as early as possible, otherwise it will affect the normal development of children’s jaws and face. (2) premature extraction of milk teeth due to caries and other reasons, the teeth on both sides of the missing teeth will move to the missing teeth, so that when the permanent teeth erupt in the future due to insufficient space and misalignment, crowding; therefore, early loss of milk teeth should be done in a timely manner to “gap retainer”. (3) Children’s bad oral habits during the period of milk teeth, such as finger sucking, lip biting, etc., may cause malocclusion and should be corrected in time. (2) Around 6-12 years old is the period of tooth replacement of children, which is called the period of tooth replacement. Many malocclusions occur in this period, so this period should pay attention to observation, find problems, timely treatment, it is best to receive regular checkups by dentists. 3.Around 11-12 years old, the replacement of all teeth is completed, and this is the permanent teeth. At this time, because the growth and development has not yet stopped, the correction of some bone malocclusion is very ideal. Most of the malocclusion can be corrected at this time. If we wait until the growth and development is completed at the age of 16-18 years old, some bony malocclusion will have to resort to surgical treatment.