A novel H3PW12O40 deposited chitosan coated iron oxide magnetic core-shell nanocomposite (Fe3O4@CS@HPW) was prepared via a facile approach. Fe3O4 nanoparticles were first coated with crosslinking-agent-free chitosan, and then H3PW12O40 was loaded onto the surface of chitosan as an outer shell. The resultant nanocomposite was well characterized by Brunauer-Emmett-Teller surface area analysis (BET), inductively coupled plasma analysis (ICP), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and elemental mappings. Fe3O4@CS@HPW showed better catalytic performance than its counterpart with a chitosan-crosslinked shell in the Friedel-Crafts acylation of anisole to 4-methoxyacetophenone under solvent-free conditions, and can be easily separated by an external magnetic field and recycled effectively.