Abstract: The preparation of the magnetic Fe₃O₄-TiO₂ nanoparticles with a core-shell structure，and investigation of their photocatalytic properties are reported in this paper.The magnetic Fe₃O₄ nanoparticles were synthesized by co-precipitation method in the presence of the surfactant，and coated with the shell of TiO₂ to form the core-shell structure of catalysts.The prepared material was characterized by the transmission and scanning electron microscopy，and the photocatalytic property was evaluated using Rhodamine B (RB) as the model molecule.The prepared Fe₃O₄-TiO₂ nanoparticles showed good magnetic property at room temperature under the external magnetic field，and could be separated from the solution easily and effectively.The RB molecules could be decomposed by the catalyst under the irradiation of UV light.The Fe₃O₄-TiO₂ nanoparticles are a new type of potential nanomaterial for the separation，concentration，and decomposition of organic or drug molecules.