Monodisperse a-Fe2O3 particles with different particle size (ca. 62010 nm or 604 nm) have been successfully prepared by hydrothermal method in short periods. In this process, the crystal-growing inhibitor (DBS) favored the formation of monodisperse nanoparticles. Monodisperse a-Fe2O3 particles with different particle size (ca. 62010 nm or 604 nm) have been successfully prepared by hydrothermal method in short periods. In this process, the crystal-growing inhibitor (DBS) favored the formation of monodisperse nanoparticles.