A modified method to prepare chitosan-poly(acrylic acid)(CS-PAA) polymer magnetic microspheres was reported in this paper. First, via self-assembly of positively charged CS and negatively charged Fe3O4 nanoparticles, magnetic CS cores with a large amount of Fe3O4 nanoparticles were successfully prepared. Subsequently, the AA monomers were polymerized on the magetic CS cores based on the reaction system of water-soluble polymer-monomer pairs. These polymer magnetic microspheres had a high Fe3O4 loading content, and showed unique pH-dependent behaviors on the size and zeta potential. From the magnetometer measurements data, the CS-PAA polymer magnetic microspheres also had superparamagnetic property as well as fast magnetic response. A continuous release of the entrapped ammonium glycyrrhizinate in such polymer magnetic microspheres occurred, which confirmed the potential applications of these microspheres for the targeted delivery of drugs. (c) 2006 Elsevier Ltd. All rights reserved.