A magnetite (Fe3O4) powder composed of uniform sub-micrometer spherical particles has been successfully synthesized by a hydrothermal method at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and galvanostatic cell cycling are employed to characterize the structure and electrochemical performance of the as-prepared Fe3O4 spheroids. The magnetite shows a stable and reversible capacity of over 900mAhg−1 during up to 60 cycles and good rate capability. The experimental results suggest that the Fe3O4 synthesized by this method is a promising anode material for high energy-density lithium-ion batteries.