(A) local harm 1, affect the development of the combined jaw surface: in the process of children’s growth and development, due to malocclusion will affect the normal development of the combined jaw surface soft and hard tissues. If the anterior teeth are not treated in time, the lower dental arch restricts the development of the front jaw, and the lower jaw does not have a coordinated relationship between the upper and lower dental arches and excessive forward development, which forms a sunken middle 1/3 of the face and mandibular protrusion deformity, with the seriousness of the malocclusion, the face presents a crescent-shaped facial shape. One side of the posterior teeth are anticlinal or misaligned causing facial development asymmetry. 2, affect the oral health: the misaligned teeth are crowded and misaligned because it is not easy to self-clean and good for caries and periodontal inflammation of gums, and often cause periodontal damage due to the misalignment of teeth. 3, affect the oral function: serious malocclusion can affect the normal function of the oral cavity, such as abnormal pronunciation caused by anterior teeth opening and closing; posterior teeth locking together can affect the chewing function; serious mandibular protrusion can cause abnormal swallowing; serious mandibular recession can affect normal breathing. Severe malocclusion can affect the function of the oromandibular system, such as the opening and closing of the anterior or posterior teeth can reduce the chewing efficiency. It has been studied that the chewing efficiency of An III bony malocclusion is reduced by 40% compared with normal fit. Malocclusion can cause abnormal tongue position, which changes the tongue-dental position relationship in all phases of swallowing activity and makes the swallowing function abnormal. It can affect the articulation when the anterior teeth are open and the mandible is protruding, mainly manifested by the lower frequency limit of consonants with abnormal articulation. The frequency distribution range becomes wider and the low frequency component increases. If the malocclusion appears to interfere with the early contact, the limits and trajectory of the opening and closing of the jaw, the anterior extension and lateral movement will be abnormal. Further will affect the function of the temporomandibular joint and organic lesions. 4, affect the appearance of appearance: all kinds of malocclusion can affect the appearance of appearance, can present open lips and teeth, double jaw protrusion, long face or short face and other deformities. (B) systemic hazards Malocclusion not only causes local hazards to the teeth and jaws craniofacial and can also cause hazards to the whole body, such as indigestion and gastrointestinal diseases caused by reduced masticatory function, in addition, due to facial deformity for patients can cause serious psychological and mental disorders.