Malocclusion is a developmental malformation that is caused by various factors during growth and development. The etiology is very complex, generally caused by genetic and environmental factors. According to the survey statistics, 60% to 70% of the malocclusions are caused by acquired environmental factors. Therefore, most of the malocclusions can be prevented, and the following should be done: Solve the malocclusions caused by heredity from eugenics. Attention to maternal nutrition and health care and prevention of maternal diseases are prerequisites for normal development of the fetus. Prevent trauma during labor when the fetus is born. Pay attention to the feeding of infants and young children. It is very important to feed infants and young children reasonably and adopt correct feeding posture. Advocate breastfeeding, artificial feeding, it is best to use the nipple close to the mother’s nipple, the opening of the nipple should not be too large, the diameter of 1 ~ 2 mm is appropriate. Children can chew food, should eat some slightly hard and easy to digest food to exercise the chewing muscles, to promote the development of chewing organs. Pay attention to the physical and mental health of young children, strengthen nutrition and pay attention to oral hygiene. Timely detection and treatment of systemic diseases, such as rickets, indigestion, endocrine disorders and chronic inflammation of the nasopharynx. Protect milk teeth and fill them as soon as possible if caries is found. Don’t pull out milk teeth easily, the integrity of milk teeth is very important for the normal eruption of permanent teeth and the establishment of occlusion. Correct the bad habits of infants and young children (e.g. mouth breathing, biting the lower lip, tongue spitting habits and sideways chewing habits, etc.). The first thing is to remove the cause of bad habits, the occurrence of a short period of time, the duration of the bad habits, after the parents to guide the reminder and patience to persuade, it is not difficult to correct. If necessary, various bad habit breakers can be used to help children overcome bad habits.