Spherical alumina support with magnetic core of 134 nm in diameter was prepared by the controlled hydrolysis of aluminums iso-propoxide. The magnetite Fe3O4 nanoparticles were first synthesized by coprecipitation. Later silica film was coated onto the surface of Fe3O4 nano particles with the sodium silicate acidification method. Alumina was supported on Fe3O4/SiO2 film by the controlled hydrolysis of aluminum alkoxide in a dilute solution consisting of cyclohexane and 2-propanol. Finally, magnetic alumina supported palladium catalysts were prepared by microemulsion method. The surface morphology and crystal structure of the magnetic alumina and catalysts were characterized by XRD, TEM, BET, and VSM, respectively. The results showed that these kinds of composite particle exhibit superparamagnetic behavior with zero coercivity and remanence. The catalysts show high activity for nitrobenzene directly hydrogenating to aniline under mild conditions. (C) 2008 American Institute of Chemical Engineers.