Bad oral habits are an important cause of malocclusion, accounting for about 1/4 of the causes of malocclusion. common bad oral habits are: 1. finger-sucking habits: most infants generally have finger-sucking habits when they are 3-4 months old and disappear around two years old. Children with long-term finger-sucking habits can cause anterior teeth open jaw, upper front teeth protrusion, narrow dental arch. 2, tongue bad action habits: children often use the tongue to lick the loose milk teeth or permanent teeth that just erupted, the tongue on the teeth outward force increases, so that the forces inside and outside the dental arch is not balanced, the front teeth tilt to the lip side, the gap appears, causing the front teeth to open the teeth together. If the tip of the tongue is often placed between the upper and lower teeth, it will also prevent the eruption of permanent teeth, forming a local open-tooth combination, jaw protrusion or even anti-dentition. 3, lip biting habits: lip biting habits mostly occur between 6-15 years old, often due to children after being criticized by teachers or parents, appear bad mood, or imitate others appear lip biting action, such as biting the lower lip habits, can cause the upper front teeth protrusion, lower front teeth crowding, open lips and teeth, jaw retraction. If there is a habit of biting the upper lip, it can cause anti-and. 4, side-chewing habits: because one side of the teeth suffering from dental caries or missing, or poor bite relationship, children will be willing to chew with the other side of the teeth for a long time, so that when chewing the jaw often to the chewing side of the movement, for a long time so that the facial development is not symmetrical. 5, biting habits: children bite hard objects such as pencils for a long time, which will form small local openings, resulting in no contact between the upper and lower front teeth when biting, affecting chewing function, pronunciation and facial appearance. 6, cheek habits: children in thinking about the problem, the habit of using the hand to one side of the cheek, or in sleep will elbow, fist pillow under one side of the face, will make the dental arch and facial development asymmetrical. For children with bad habits, attention should be paid to early detection and early correction, and parents should take the initiative to care and remind them at any time, so that the children’s teeth and face can develop normally. The already formed malocclusion should be orthodontically treated as early as possible.