Nanoporous Fe3O4 magnetic microspheres have been successfully synthesized by the way of microwave heating. The experimental process is expeditious, simple and environmentally friendly. The obtained sample is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller analysis (BET), Fourier transform infrared (FT-IR), high-resolution transmission electron microscopy (HRTEM) and magnetic measurements. The average size of Fe3O4 microspheres is ∼100nm and shows well-dispersed quality in aqueous solution. More importantly, the microspheres possess both nanoporous structure and superparamagnetic behaviour, which endow them powerful application potentials in chemical, biological/biomedical, physical and environmental engineering fields, for example, catalyst or drug carrier, absorption, separation and contrast agents, etc.