Large-area one dimensional (1D) alpha-Fe2O3 nanostructures were grown on iron substrates by catalyst-free thermal oxidation process at low temperatures in air. The structure characterization revealed that the nanostructures are single crystalline alpha-Fe2O3. Two kinds of alpha-Fe2O3 nanostructures, nanobelts and nanoflakes, were obtained due to the different growth temperature range. A surface diffusion mechanism is proposed to account for the nanobelts and nanoflakes growth. The Morin temperature T(M) of pure 1D alpha-Fe2O3 nanostructures is 121 K, which is far below their bulk counterparts. The coercive field depends on temperature, and takes values 471 Oe at 5 K and about 260 Oe when the temperature is greater than T(M), respectively.