Dentofacial deformities can appear as early as 3~4 years old, which shows that deciduous teeth cover the sky. At this time, non-surgical orthodontic treatment can be given, which relieves the restriction of lower deciduous teeth on maxillary growth and avoids aggravating jaw deformity. 7~ 12 years old is another opportunity to correct secondary jaw deformity. At this time, the maxillary growth can be promoted by wearing a traction device.