Mouth breathing in children is caused by physiological factors, but can also be caused by pathological and psychological factors, and can be corrected by correcting bad habits, surgery and orthodontic methods. Children occasionally breathe through their mouths during exercise, but for a short period of time, and can naturally return to nasal breathing without adversely affecting their maxillofacial growth. Mouth breathing in children is often caused by upper respiratory tract infections, enlarged adenoids, enlarged tonsils, mouth closure disorders, long-term bad habits and stress and anger. For different causes, the method of correcting mouth breathing is also different. 1. Correct bad habits: upper respiratory tract infections can lead to nasal obstruction, some children will be compensated by mouth breathing, but the duration is short, when the infection is under control, nasal breathing can be resumed. If a child’s habit of mouth breathing is not corrected, it can be corrected by educating the child not to breathe through the mouth and, if necessary, using orthodontic methods. 2. Surgery: When children have enlarged adenoids or enlarged tonsils, nasal breathing can be obstructed and they are forced to breathe through their mouths. In this case, it is necessary to surgically remove the oversized adenoids or tonsils, and after the blocked nasal passage is cleared, then orthodontic correction will be carried out as appropriate. 3. Orthodontic treatment: after removing the acute or chronic nasal respiratory diseases and psychological factors that lead to nasal obstruction, children who still have the habit of mouth-breathing can be corrected through functional orthodontic appliances, such as vestibular shield, bimaxillary pad orthodontic appliances, etc. When children experience mouth-breathing, they should be treated promptly. When mouth breathing occurs in children, they should seek prompt medical attention to prevent malocclusion, oral mucosal diseases, and cardiovascular diseases caused by mouth breathing.