Novel magnetic-nanometer titanium dioxide/ferriferous oxide (TiO2/Fe3O4) composite photocatalyst was prepared using acid-sol and homogenous precipitation methods. The photocatalyst particle was made of a Fe3O4 core covered with nanocrystal anatase TiO2, without a high-temperature heat-treatment step. The catalyst has been characterized by X-ray diffraction, transmission electron microscopy, differential thermal analysis measurements, and ultraviolet spectrum. The results suggested that titania was mainly presented as anatase and Fe3O4 did not appear on the surface of the composite particles when the molar ratio of TiO2/Fe3O4 increased to 20:1 in the acid-sol method, but 5:1 in the homogeneous precipitin method. The size of the crystal was ranged from 2.4 to 3.6 nm prepared by both methods. In the catalytic test, the composite particles, which were prepared by acid-sol, had higher catalytic activity than that prepared by homogenous precipitation method due to the size difference of the composite particles.