Nanopowders of single-crystalline rod-like magnetite have been synthesized in a glycerol-water system under hydrothermal condition by using the goethite (a-FeOOH) precursor. The influence of different reaction parameters on the morphology and composition of the products have been investigated. The structure, morphology and magnetic properties of the products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM) and superconducting quantum interference device (SQUID). The results show that every as-prepared Fe3O4 nanorod with diameter ca. 70nm grows along the [110] direction which is one of easy magnetic axes of magnetite. The ratio of glycerol to water has a great effect on the purity at given temperature. Magnetic measurements indicated that the specific saturation magnetization (M-s) and coercivity values (H-c) of magnetite nanorods were 90 emu/ g and 172Oe, respectively. An in situ dissolution-reduction-reassembling formation mechanism is recommended for as-synthesized magnetite nanorods.