Fluor-hydroxyapatite (FHA) powder was synthesized using polyacrylamide gel method with Ca(NO3)2•4H2O as raw material of calcium, (NH4)2HPO4 as raw material of phosphor, and different amounts of ammonium fluoride (NH4F) acting as fluorine source. XRD and FT-IR results showed that, the F- enter the crystal lattice of hydroxyapatite and substitute for some of the OH-, and result in the change of the symmetry of crystal structure. As the fluorine addition was increased, the a-axis of the apatite decreased gradually while the c-axis does not obviously changed, and the content of the β-TCP decreased gradually. So addition of fluorine ions effectively suppresses the decomposition and enhances the thermal stability of pure HA. The lattice parameter has a good liner relationship with fluorine content: a = -1.29×10-3 x + 0.94063; c = 4.3×10-4 x + 0.68772(R2≥0.95). But addition of F- has no effects on microstructure of HA, and fluorine-substituted hydroxyapatite remains hexagonal morphology.