We developed a versatile method using alkylamines (octylamine and isobutylamine) as structure-directing agents for synthesis of various 1D transition metal oxides in aqueous solution. In this report, 1D iron and copper oxide precursors (for simplicity, we have denoted them as pre-Fe 2O3 and pre-CuO) and ZnO were prepared. After calcination and reduction, the 1D nanostructure of pre-Fe2O3 can be easily converted to 1D α-Fe2O3 and 1D Fe 3O4, successively. The aspect ratio of the 1D nanostructures increases with the reaction time. XRD, TEM, in situ TEM, and TGA were used to characterize the samples. Results showed that after calcination at temperatures higher than 300°C, the as-prepared 1D pre-Fe2O 3, which was polycrystalline, transformed into 1D single-crystalline α-Fe2O3. A mechanism of assembling and "packing" along a certain direction for the growth of the 1D nanostructure was confirmed.