Fe3O4/TiO2 composite nanoparticles (NPs) were synthesized by a reverse micelle microemulsion method with Igepal CO-550 as a stabilizer. Annealed samples have distinct two stage band gap energies of 3.2 and 2.1 eV. In addition to the optical red-shift effect of absorption band, Fe3O4/TiO2 composite NPs maintain soft ferromagnetism with saturation magnetization of 36 emu g(-1) at room temperature, which makes them heterogeneous catalysts for the photochemical reactions.