Introduction: Micro/nanostructured materials have attracted a great deal of attention, and many strategies have been developed to fabricate micro/nanostructured materials. Methods: Amine-functionalized micro/nanostructured Fe3O4 with different sizes was synthesized conveniently in organic media. The chemical structures of as-synthesized products were characterized by FTIR, TEM, SEM, and XRD. Results: The ligand binds to the Fe3O4 core by hydrogen bond between the oxygen atom on the surface of Fe3O4 and the hydrogen atom in molecular ethylenediamine. Their magnetic properties were also investigated. Conclusions: First, there is no need to control the reaction under a nitrogen atmosphere, and just one salt is used as an iron source. The growth and the surface modification of Fe3O4 crystalline nucleation happen at the same time. Second, monodispersed Fe3O4 micro/nanospheres were prepared without additional surfactant or external magnetic fields. Third, this method is preferred compared with the conventional organic phase method, as the reaction condition is milder and less pollutant will be produced.