Abstract: In order to utilize the magnetic responsiveness of Fe₃O₄ and the excellent photocatalytic activity of graphite carbon nitride (g-C₃N₄), high temperature thermal polymerization method was used to prepare g-C₃N₄ with urea as a precursor. The magnetic separation Fe₃O₄/g-C₃N₄ composite photocatalyst was synthesized by hydrothermal method. The obtained samples were characterized by TEM, XRD, TGA, BET and vibrating sample magnetometer (VSM) to investigate the morphology, crystalline phase, specific surface area, composition and saturation magnetization of Fe₃O₄/g-C₃N₄ composites. The adsorption and photocatalytic properties of Fe₃O₄/g-C₃N₄ composites were evaluated by the adsorption and photocatalytic degradation of dye methylene blue (MB) under simulated sunlight. The results show that the specific surface area of magnetic separation Fe₃O₄/g-C₃N₄ composites is large compared with g-C₃N₄, up to 71.89 m²/g. Fe₃O₄/g-C₃N₄ composites possess good magnetic, and the intensity of saturation magnetic field reaches to 18.79 emu/g, which is enough for magnetic separation and recovery. The removal rate of MB reaches to 56.54% under irradiation for 240 min. Fe₃O₄/g-C₃N₄ composites not only exhibit good adsorption and photocatalytic activity and magnetic, but also can be recovered easily by external magnetic field.