Magnetic composite Fe3O4/TiO2/CuO nanoparticles have been synthesized by sol-gel method at low temperature. The resultant composite nanoparticles coupled with different Cu contained by adjusting the molar ratio of CuO to (Fe3O4/TiO2) from 1:1 – 5:1. The structure, morphology and properties of nanoparticles were characterized using XRD, EDX, FESEM and VSM. The results showed that all composite nanoparticles consist of cubic spinel Fe3O4, anatase TiO2 and monoclinic CuO, have ferromagnetic properties. The photocatalytic performance was evaluated using methylene blue in aqueous solutions under UV and visible light irradiation. Among the composite Fe3O4/TiO2/CuO nanoparticles, the sample with the molar ratio of CuO to (Fe3O4/TiO2) = 5: 1 exhibited the highest photocatalytic efficiency. Photocatalytic mechanism was investigated by measuring the photocatalytic degradation rate in the presence of scavenger. The results suggested that holes play the most important role in degradation of methylene blue.