Natural biological hard tissues are nanocomposites of proteins and calcium hydroxyapatite (HAp) with superior strength and bioresorbabilities. Nanometer scale hyroxyapatite is the key material to manufacture bioresorbable bone substitute. An attempt was conducted to synthesis nano-crystalline hydroxyapatite with a hydrothermal chemical method. The prepared nano-crystalline HAp was characterized for its phase purity and nanoscale morphological structure by XRD, TEM and FTIR. The obtained results indicated that hydrothermal synthesized nano-crystalline HAp was pure single phased HAp with a diameter of 20 to 50nm and length range between 50 to 200nm and each HAp particle was observed to be a monocrystal of HAp. It’s suggested that hydrothermal treatment may be an effective method to get pure and nice crystallized nano-sized stoichiometric hydroxyapatite.