The microradiography SEM and TEM were used ton observe histopathological changes in dental fluorasis with various degrees in this study.The characters of histopathological changes of dental fluorasis are:(1) the lesios appear in exterior layer of enamel,not excess one third enamel.(2)the future of the lesion is enamel-hypoplasia,enamel rods were hypomineralized.the space among enamel rods widen and form some cavities.There are a lot of spaces in intercrystlines.Many micropores and injures exhibit on enamel surface.(3)the clinic severe degree of lesion is similar to the histopathological changes.It could be indicated using the Dean's and the TF index.