The location of decay of milk teeth in the process of growth has a great relationship with the time, and the decay occurs in different locations at different times. At the age of 1-2 years old, the caries of the child occurs in the front teeth, which is caused by drinking bottle, and the caries of the front teeth mainly occurs in the lip and tongue; at the age of 3-4 years old, the caries of the milk teeth mainly occurs in the back teeth, the back milk molar, and the milk molar’s sulcus is not frequently cleaned with food residue, which will cause the caries in the sulcus. At the age of 5-6 years old, due to the development of jaw bone, the gap between teeth will gradually increase, and the location of caries occurs between the two teeth of the posterior molar, and the adjacent teeth will be easily embedded with food, and caries will occur. Parents must be vigilant, don’t think that it’s okay if the child looks fine on the surface, many children only find out when the caries is decayed, and the caries between the two teeth can be so bad.