The main purpose of fluoride application for children is to prevent tooth decay, or to have some remineralization effect on the relatively early caries, which can prevent further aggravation of tooth decay. Fluoride ion interacts with hydroxyapatite in the enamel to form fluorapatite, which is more resistant to acidity and will make the teeth more resistant to caries. Now for some children, we can apply fluorine on the surface of teeth to enhance the ability to resist caries and prevent the occurrence of dental caries, which can make the early caries have some remineralization effect and slow down the speed of tooth decay. Therefore, nowadays, we can consider to apply fluoride on the surface of teeth to prevent caries for children.