A facile strategy for grafting poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) on the surface of hydroxy carbonate apatite (HCA) nanoparticles via surface-initiated ATRP has been presented. SEM, FT-IR, TGA, N-2 adsorption-desorption analysis, and DLS were employed for their characterization. The results demonstrated that the stimuli-responsive polymer had been successfully grafted onto the surface of HCA. The stimuli-responsive brushes attached to HCA could act as a switch to control the opening and closing of the pore on the surface of HCA. In this paper, the pH-responsive property was mainly focused on.