Malocclusion is a malformation of the teeth, jaws and craniofacial surface caused by congenital genetic factors and acquired environmental factors during the growth and development of children. Specific as follows: 1, congenital genetic factors: the wrong (dental) malformation is mainly due to congenital genetic factors, including racial evolution and individual development. Racial evolution is mainly due to human upright walking, so that the jaw bone degeneration, as well as muscle degeneration and dental degeneration, due to unbalanced degeneration, that is, the degeneration of the jaw bone is better than muscle degeneration, better than dental degeneration, and finally lead to the emergence of crowded teeth, maxillary protrusion, anti (teeth together) and other wrong (teeth together) malformation. Individual development is due to the mother, father or the previous generation, some dental irregularities, skeletal deformities will be inherited to the child through genes; 2, environmental factors, environmental factors including congenital environmental factors and acquired environmental factors, congenital environmental factors including the mother’s factors, when the mother is pregnant with the fetus due to drugs, disease, their own body malnutrition, resulting in the child’s mis(dentition) malformation, while the fetus Fetal malocclusion can also be caused by trauma, unexplained extrusion, or poor nutrition in the mother’s body. The environmental factors also include dental replacement disorder, the child does not lose the milk teeth or the permanent teeth erupt early when the teeth are replaced, as well as bad oral habits, lip habits, tongue habits, abnormal swallowing and mouth breathing are the main factors that cause malocclusion.