Objective To analyze the mechanism of fluorine by systemic analysis of fluorination-demineralizationremineralization experiments. Methods The enamel specimens were randomly assigned to untreated group（group A）, non-fluoride group（group B）, low-fluoride group（group C） and high-fluoride group（group D）. The in vitro model of fluoride enamel was established in group C and D. Based on that, the establishment of demineralization model and remineralization experiment by pH-cycling in group B, C and D were followed. All enamel specimens were observed by stereomicroscope and scanning electron microscope and compared in surface microhardness value. Results There was distinct difference in micro-morphologic appearance on fluoride enamel surface. Artificial caries of fluoride enamel showed a relatively complete surface, the surface microhardness after demineralization and remineralization in fluoride group was higher than non-fluoride group（P
