By employing microwave irradiation as a heat source, magnetite/graphene composites were synthesized by depositing Fe³⁺ in the interspaces of graphene sheets. The Fe₃O₄ nanoparticles were dispersed on graphene sheets. As anode materials for lithium ion batteries, they showed high reversible capacities, as well as significantly enhanced cycling performances (about 650 mA h g⁻¹ after 50 cycles) and high rate capabilities (350 mA h g⁻¹ at 5 C). The enhancement could be attributed to graphene sheets, which served as electron conductors and buffers. Our results opened a new doorway for the application of graphene sheets to prepare anode materials of lithium ion batteries with superior performances.