Abstract: The surface modification of nano-hydroxyapatite with stearic acid was studied. The nano-hydroxyapatite/polycarbonate composite biomaterial was prepared. The samples were characterized by TEM , FTIR , XRD and SEM techniques. The results show that the stearic acid bound on the surface of nano-hydroxyapatite particles by forming an organic coating layer . The interface compatibility of polycarbonate and hydroxyapatite was improved through their interface integration by the hydrogen bond. The mechanical properties of the composite are found to match well with those of a natural bone.