Tooth decay is commonly known as worm teeth or tooth decay. Under suitable conditions, the food residues on the teeth will be fermented by bacteria to produce acid. The main component of tooth is calcium, after calcium encounters certain concentration of acid, it will be dissolved, softened, decalcified and destroyed gradually after a period of time, and finally cavity will appear, from big to small, from shallow to deep. If it is allowed to develop, it can corrode all the crowns of the teeth. When tooth decay develops to a certain degree, food will be embedded in the cavity or painful when eating, thus affecting appetite and causing paranoia and anorexia. In order to avoid the pain, children will not chew on the side with caries, which will form the bad habit of chewing on the side and cause the asymmetry of facial development. If the chewing is reduced because of tooth decay, the dental bed and jaw bone will not get the proper physiological stimulation and affect the development, which will cause different degrees of tooth misalignment and jaw and face deformation in the future. If the decay of baby teeth is not treated in time, it will easily lead to the early loss of teeth to form a gap. The adjacent teeth will be shifted to the gap, resulting in insufficient position of the inherited permanent teeth when they erupt, leading to the disorder of the occlusal relationship. If the tooth decay occurs in the front teeth, it will not only affect the beauty, but also cause the speech to run wind, affect the normal pronunciation of the child, and even affect the physical health of the child. Therefore, parents should cultivate children’s habit of rinsing their mouth after meals and brushing their teeth in the morning and evening from childhood. Teach children the correct way to brush their teeth. Establish the awareness of oral health care, do oral examination every 3~6 months, timely prevention, early detection and early treatment.