Limestone is made of calcium carbonate. An Attempt is made to convert calcium carbonate to calcium oxide for precursor of calcium in hydroxyapatite synthesis. Phosphate was from hydrogen phosphate [H3PO4]. Diammonium hydrogen phosphate [(NH4)2HPO4] were used as precursors and ammonia was used as the agent for pH adjustment. The synthesized samples was characterized by Fourier Transform Infra Red (FTIR), X-ray Difraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Result show that hydroxyapatite with calcium oxide 1 M was give fine produce. Analysis of BET, result show Intercept of 1.174e+01 and slope of 250.030, total pore volume obtained from hydroxyapatite 3.881e-02 cc/g and average pore radius of 5.83490e+01 Å.