Nanoparticles hydroxyapatite (HAp) had been synthesized from limestone by using hydrothermal method. Precursors were limestone (CaCO3) and diammonium hydrogen phosphate ((NH4)2HPO4) with 1.67 ratio of Ca/P. Hydroxyapatite (HAp) was obtained by mixing precursors at pH 10 in variation temperature at 120, 160 and 200°C. The product were characterized by Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). FTIR was used to determine phosphate and hydroxyl functional groups as the constituent group of hydroxyapatite. XRD data showed that all of products were hydroxyapatite. Hydroxyapatite synthesized at 200°C has smaller crystal size than others. SEM images showed that nanoparticles hydroxyapatite had spherical shape.