Tooth decay of milk teeth is the most common oral disease of children, the caries rate of 5-year-old children in our country is 66%, of which 97% are not treated; the caries rate of permanent teeth of 12-year-old children is 28.9%, of which 89% are not treated. There are three main reasons for children’s caries: 1.Children’s food is mainly sticky food with high sugar, high protein and high energy; 2.Insensible to brush teeth; 3.Children sleep for a long time, saliva secretion is little, food residue is easily attached to the tooth surface. After understanding the causes of children’s milk teeth prone to caries, we know how to better prevent the occurrence of milk teeth caries.