Uniform single-crystal Fe 3 O 4 nanorods with an average diameter of 25nm and length of 200nm have been synthesized via a soft-template-assisted hydrothermal route at 120°C for 20h. The magnetic properties of as-prepared samples were recorded on a vibrating sample magnetometer (VSM) at room temperature. The hysteresis loop of Fe 3 O 4 nanorods shows a ferromagnetic behavior with saturation magnetization of 71.3emu/g and coercivity of 150Oe. The formation of one-dimensional (1D) Fe 3 O 4 nanostructures could be ascribed to ethylenediamine. It is revealed that ethylenediamine plays a crucial role not only as a base source but also as a soft template to form single-crystal Fe 3 O 4 nanorods, and the benzene used in this study is important to prevent ferrous ion to be oxygenated by oxygen in air.