A kind of magnetic Fe3O4@Agarose microsphere (MAM) with a core-shell structure, large volume shrinkage and high stability in acidic solution was synthesized to remove radionuclides from aqueous solutions. The structure, magnetic and surface properties of MAM were characterized by microscope, Fourier transform infrared (FTIR) spectroscopy. vibrating sample magnetometry (VSM) and thermo gravimetric analysis (TGA). The agarose-functionalized MAM exhibits high sorption capacities of 1.151 mmol/g for U(VI) and 1.276 mmol/g for Eu(III) through the formation of strong complexes of radionuclides with abundant hydroxyl groups in the molecular chain of agarose. The radionuclide-loaded MAM could be recovered from aqueous solution by magnetic separation. Moreover, the volume of the MAM sample could shrink down to about a twentieth of the wet sample when dried, which is easy to be sealed and deposited. The findings of this present work highlight the potential using of MAM as an effective and safe adsorbent for the removal and preconcentration of radionuclides from wastewater. (C) 2011 Elsevier B.V. All rights reserved.