Several hydroxyapatite powders were prepared by wet chemical precipitation route at 25ï°C in presence of different concentration of silicate and sulfate. The powderswere characterized using chemical analysis, SEM,XRD and FTIR spectroscopy. The substitution of sulfate ion in the structure of HAP raised silicate substitution up to 9.9 % wt. Increasing silicate and sulfate ions substitutions are associated with increasing carbonate ion substitutions for phosphates and vacancies in the OHÂ site. Silicate and sulfate substitution took place via three charge compensation mechanism acting simultaneously. The first is; SiO4 4Â group substitute one PO4 3Â group and vacancy formin the OH- site. The second is; SiO4 4- and SO4 2Â groups substitute two PO4 3Â groups. The third is; SiO4 4- and CO3 2Â groups substitute two PO4 3Â groups.