砄bjective: To compare the effects of compound fluoride preparation(Co F) on the inorganic phases of the teeth with those of ZnF 2 .Methods: Synthetic hydroxyapatite(HA) was immersed into Co F containing ZnF 2, SrF 2. LiF and CaF 2, and with F - concentration of 3 500 mg/L, or into saturated ZnF 2 solution with F - concentration of 3 200 mg/L or into NaF solution with F - concentration of 3 500 mg/L for 1 and 10 days respectively. Fluoride absorption into HA was measured by X ray diffraction analysis. Results: F - absorption (?g/g) of HA in NaF solution for 1 day and 10 days were 781.81?94.38 and 805.25?87.11; that in ZnF 2 5 764.93?726.58 and 7 177.33?1 498.37, in Co F 4 901.68?680.02 and 7 136.19?461.56, respectively. KOH F(?g/g) of HA in NaF solution for 1 and 10 days were 94.96?8.28 and 151.10?19.79, that in ZnF 2 230.8?25.08 and 6 576.89?1 440.17, in Co F 1 168.18?69.42 and 4 336.72?363.16, respectively. Conclusion: ZnF 2 contained in the Co F is very important in respect of the increase of fluoride absorption.