With the improvement of people’s living standard, the diet structure has changed, especially the consumption of sugar has increased, which makes the risk of caries in children increase. The caries rate of milk teeth of 4, 5 and 6 years old children in Beijing is over 70%, 80% and 90% respectively, while the treatment rate of these children is very low, only about 1% – 8%. The high caries rate of preschool children’s milk teeth is becoming a serious social problem, and the serious lack of dental resources makes this contradiction more prominent. Therefore, it is urgent to do a good job in the prevention and treatment of caries. The successful experience of developed countries shows that caries can be completely prevented. The key to the occurrence of caries is that the sugars in food are used by bacteria to produce acid and cause tooth demineralization. We should take comprehensive preventive measures for the conditions of caries occurrence. The prevention of caries mainly starts from the following aspects: First of all, good oral hygiene habits. Good oral hygiene habits are good for removing plaque. The caries-causing bacteria in the mouth attach and gather on the tooth surface to form plaque, which is the key to the occurrence of caries and provides the microenvironment of demineralization. Effective brushing is the most effective means to remove plaque. The second is good dietary habits. The process of caries needs the participation of sugar, and the sugar in food provides the energy source and the raw material of acid production for the bacteria in the mouth. Minimizing the intake of sugar and choosing a reasonable way of eating is the key to control caries. Thirdly, regular oral health examination. It is conducive to the early detection and early treatment of caries. Fourthly, receive professional caries prevention measures. Including sulcus closure and fluoride caries prevention, etc.