The ultrafine Fe2O3 nanoparticles and their selfassembled nanosaucers and nanorings were successfully prepared by a simple hydrothermal method. The structure, morphology, specific surface area and optical properties of the samples were characterized by XRD, SEM, TEM, BET and UVVis. The results showed that the average diameter of ultrafine Fe2O3 nanoparticles was about 5.5 nm and the specific surface area was up to 256.2 m2·g-1. By controlling the reaction time and other experimental conditions, the prepared Fe2O3 nanoparticles can be 3D directionally assembled into a saucer shape structure and further evolved into the nanorings by etching. The surfaces of these structures were interconnected by ultrafine nanoparticles which can provide a large number of active sites for photocatalytic reaction. The photocatalytic degradation of Rhodamine B under visible light irradiation showed that the Fe2O3 nanosaucers reassembled structure had the excellent visible photocatalytic activity, stable performance and easy to recovery. These characters make ultrafine Fe2O3 nanoparticles and their reassembled structure materials have great practical value in the field of photocatalysis.