We report on the synthesis of Fe(3)O(4) nanobelts with good magnetic properties and lithium storage performances by using a one-pot and template-free hydrothermal method with Na(2)CO(3) and FeCl(2) as the reactants. By controlling the amount of Na(2)CO(3), we obtained pure Fe(3)O(4) nanobelts with widths of 0.1-2 μm, thicknesses of about 10 nm and lengths of 20-30 μm, showing a high aspect ratio. XRD and SAED patterns of the obtained sample demonstrated that the Fe(3)O(4) nanobelts were well crystallized. Nitrogen adsorption/desorption measurements showed that Fe(3)O(4) nanobelts manifested a BET surface area of 25.04 m(2) g(-1). Further experiments demonstrated that the amount of Na(2)CO(3) played an important role in controlling both the morphologies and crystal structures of the products. The formation mechanism of Fe(3)O(4) nanobelts was also studied. More importantly, we found that the Fe(3)O(4) nanobelts showed magnetic properties with a magnetic saturation value of 77.0 emu g(-1) and lithium storage performances with a high initial discharge capacity of 1090 mAh g(-1) at a current rate of 500 mA g(-1), and a reversible capacity of 404 mAh g(-1) retained after 60 charge/discharge cycles. These results suggest that the Fe(3)O(4) nanobelts might be promising for magnetic and lithium battery applications.