Drinking-water fluorosis and seawater intrusion are common phenomena along coastal zones. The groundwater property variation evoked by seawater intrusion has the potential effect on fluorine transformation of rock (soil), but it lacks the direct simulation experiments, and the mechanism of fluorine transformation is still unclear. The static simulation experiments of fluorine transformation of sediments in the aquifers were performed by simulating the seawater intrusion process with the mixture of fresh water, seawater, brine water and laboratory solutions, and the FTIR spectrum of sediments was compared. By this way, the laws and mechanism of the effect of seawater intrusion on rock (soil) fluorine transformation are expected to be detected. The results are gained as follows: the orders of the fluorine transformation ability are: seawater＞1∶1 fresh water and seawater＞fresh water, and brine water＞1∶1 fresh water and brine water＞fresh water. The more fluorine in rock(soil) transforms with the more mixture of seawater or brine water. The sediments show higher ability of fluorine transformation with the higher levels of NaCl and NaHCO3, and with the lower levels of CaCl2. The intensity of Si—O—Si stretching vibration peak increases, that of bending vibration of fluorapatite decreases, and that of O—H adsorption peak doesn’t change with the higher levels of NaCl, but the opposite case occurs with the higher levels of NaHCO3, which indicates the fluorine migration mainly by the OH--F- exchange in NaHCO3 solution and instead by Si substitution of Si—O—Si bond in NaCl solution. The intensity of Si—O—Si stretching vibration peaks is weakened and that of fluorapatite bending vibration increases with the higher levels of CaCl2, indicating that Ca2+ can restrain the rock(soil) fluorine transformation. Meanwhile, the intensity of Si-F bending variation peak decreases and Si—O bending variation peak moves towards the low wavenumber with the increase of NaCl and NaHCO3 concentrations and the decrease of CaCl2 concentration. The 1 460 and 1 420 cm-1 CO2-3 absorption peaks occur when the sediment interacts with 1 mol·L-1 CaCl2 because of the CO2 mixture. The sediment has the higher intensity of 1 460 cm-1 absorption peak and the new 875 cm-1 absorption peak when interacting with 1 mol·L-1 NaHCO3. But the sediment has no CO2-3 absorption peaks when interacting with seawater, brine water and NaCl solution. These facts indicates no fluorite (CaF2) dissolution. Thus, the alkaline, high Na+ and low Ca2+ conditions due to seawater intrusion lead to the high fluorine-leaching ability of rock(soil), which should be the important dynamics of high-fluorine groundwater along coastal zones.