Monodispersed core-shell porous Fe3O4@C nanospheres are prepared through hydrothermal treatment and subsequent chemical vapor deposition (CVD). Specially, the magnetite reduction and carbon coating are completed via CVD simultaneously and the process is verified by X-ray diffraction, scanning electron microscope and transmission electron microscope. Fe3O4@C composites exhibit high reversible capacity (∼1100 mA h g−1 at 100 mA g−1 after 60 cycles), excellent cyclic stability and good rate performance. The carbon coating layer serves as a highly conducting framework and provides a flexible space for buffering strain and stress, and the pores facilitate ion transport during electrochemical cycling. More importantly, the core-shell Fe3O4@C composite is connected by carbon to form a three-dimensional network, which contributes to the relief of inner strain and the fast transport of electrons and lithium ions.