Abstract: Carboxylate-rich carbonaceous composite materials were prepared using hydrothermal method, then magnetically modified carboxylate-rich carbonaceous composite material was prepared by chemical co-precipitation process. The morphology, contents, structures, paramagnetic properties and surface charge properties of magnetic carboxylate-rich carbon have been characterized by transmission electron microscopy (TEM), Fourier transformed infrared spectrum (FTIR), X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), zeta potential and specific surface area (BET), and sorption of Pb(Ⅱ), Ni(Ⅱ), Hg(Ⅱ) and U(Ⅵ) by carboxylate-rich carbon and magnetic carboxylate-rich carbon was also studied. Results indicate that Fe₃O₄ nanoparticles are absorbed to the surfaces of magnetic carboxylate-rich carbon. Its surface area increases from 29.2 m²/g to 45.4 m²/g. The introduced Fe₃O₄ improves thermal stability. The saturation magnetization of magnetic carboxylate-rich carbon is 30.68 A·m²/kg. The equilibrium sorption capacities of Pb(Ⅱ), Ni(Ⅱ), Hg(Ⅱ) and U(Ⅵ) on magnetic carboxylate-rich carbon are 477.50, 23.50, 260.20 and 54.86 mg/g, respectively, which are lower than carboxylate rich carbon. The Langmuir isotherm is the best-fit sorption isotherm model. From the high sorption capacities of Pb(Ⅱ), Ni(Ⅱ), Hg(Ⅱ) and U(Ⅵ) on magnetic carboxylate-rich carbon and comparison of U(Ⅵ) sorption capacities on different sorbents, magnetic carboxylate-rich carbon is a promising sorption material for water treatment of heavy metal ions and radionuclides.