Magnetite (Fe3O4)/expanded graphite (EG) composite material is prepared through the oxidation progress of ferrocene–graphite intercalation compound in acetone solution. The reactions occur in this system and lead to in-situ synthesis of the composite with nanosized magnetite and expanded graphite. Due to the lithium insertion/extraction experiment, the Fe3O4/EG composite material shows high reversible capacities (ca. 720 mA h g−1 at 120 mA g−1 charge current) and excellent rate performances (ca. 630 mA h g−1 at 600 mA g−1, 420 mA h g−1 at 6000 mA g−1 and 360 mA h g−1 at 9000 mA g−1charge current). Owning to the strong interaction between Fe3O4 and EG from in-situ synthesis, it is demonstrated that these properties of this novel Fe3O4/EG composite material will be an idea candidate for the negative electrode material of high-current lithium ion battery.