Abstract: Objective To examine the influence of fluorine ion metablism on the formation of fluorotic teeth by observ ations of the changes of urine fluorine,blood fluorine,fluorine in bone,and tooth slice after exposures to different concentrations of sodium fluoride in rat. Methods Wistar female rats were randomly divided into 5 groups which exposed to 0,25, 50,100,and 150 mg/L fluorine ion in drinking water for 6 months.The fluorine ion concentration of urine,blood,teeth,and bone were determined and the slice of teeth were observed with microscope. Results The increase of body weight weakened gradually after 8 weeks' exposure to fluorine ion of 150 mm/L with a significant difference compared with that of rats in contorl group(P<0.05).The contents of urine,bone and teeth fluorine increased significantly compared with those of the controls(P<0.05). Conclusion The occurrence and severity of fluorotic teeth were positively correlated with the time and dose of fluorine ion exposure.Urine,bone,and tooth fluorine and fluorotic teeth formation were positively correlated.No difinite relationship was observed between blood fluorine change and fiuorotic teeth formation.