The Fe 3 O 4 magnetic microspheres were prepared by a cetyltrimethyl ammonium bromide (CTAB) modified solvothermal process. Then CTAB-modified Fe 3 O 4 microspheres were directly coated by mesoporous SiO 2 and γ-AlOOH shell, respectively, and the SiO 2 @Fe 3 O 4 and γ-AlOOH@Fe 3 O 4 magnetic core–shell composites were obtained. The samples were characterized by FT-IR, XRD, Raman spectroscopy, SEM, TEM, N 2 adsorption–desorption technology, and vibrating sample magnetometer (VSM). The results indicate that CTAB molecules play the roles of capping agent, dispersant, and crystal growth oriented agent during the high-temperature solvothermal process. Thus as-prepared Fe 3 O 4 microspheres are assembled by small primary nanocrystals with uniform crystal orientation, and exhibit narrow size distribution, monodispersity, and superparamagnetism with high saturation magnetization (Ms). The formation of Fe 3 O 4 microspheres combines oriented attachment and Ostwald ripening mechanisms. Furthermore, the adsorbed CTAB molecules can serve as nucleation seeds for precipitation of SiO 2 and γ-AlOOH, and as templates for growth of mesoporous SiO 2 . In SiO 2 @Fe 3 O 4 the mesoporous SiO 2 shell presents short-range ordered pores with mean pore size of 2.1nm. The shell of γ-AlOOH@Fe 3 O 4 is composed of many irregular γ-AlOOH nanosheets with thickness of 3.0–5.0nm. The BET surface areas of SiO 2 @Fe 3 O 4 and γ-AlOOH@Fe 3 O 4 reach up to 441m 2 /g and 289m 2 /g, respectively.