Polymethyl methacrylate (PMMA) brushes with a quantitative molecular weight (M-w) and low polydispersity index are synthesized via atom transfer radical polymerization and grafted onto the surfaces of hydroxyapatite (HA) that were modified with gamma-methacryloxypropyl trimethoxysilane (MPTS). The structure and morphology of MPTS surface modified and furthermore PMMA grafted HA was mainly investigated by means of infrared spectrophotometry, X-ray diffraction, thermal gravimetric analysis, scanning electron microscope, and differential scanning calorimetry studies. It is found that polymer brushes are covalently attached to the HA surface under controlled M-w of PMMA segments without any structural deformation on the HA phase and exhibit grafting abilities for tuning properties of the composites.