A novel magnetically separable core/shell type nanocomposite was synthesized in a facile way and characterized by XRD, UV–Vis, FT-IR, TEM, nitrogen physisorption and magnetite susceptibility measurements. In the synthesis procedure, the mesoporous silica shell was coating on the surface of magnetic core directly via a nano-assembling method. After calcination at high temperature (550°C) for template removal, the spinel phase of maghemite core was retained without any transformation. The resulting material possessed a regularly hexagonal mesoporous structure with a high specific surface area (908.70m 2 /g), which were favorable to further functional modification. Once incorporated with iron species by in situ synthesis, the nanocomposite could serve as a Fenton catalyst and was effective in phenol degradation at the given conditions (40°C, pH=4). At the end of the reaction, it was easily collected by an external magnetic field and remained efficient in reuse.