In order to realize the fluorescence magnetic bifunctionalization of nanoparticles, a bifunctional composite material with high fluorescence superparamagnetism was successfully designed. The rhodamine B (RhB) dye was covalently coupled with polyethylene glycol (PEG), and then the polyethylene glycol-rhodamine B (PEG-RhB) was successfully bonded to the surface of the ferric oxide (Fe3O4) through the hydrogen bonding. An effective space barrier was established due to the presence of PEG, which not only prevented the agglomeration of Fe3O4 nanoparticles through the magnetic dipole interaction, but also reduced the direct contact between RhB and the surface of magnetic particles. Moreover, the chain structure of magnetic nanoparticles can be observed in real time under the condition of magnetic field-gravity field coupling, which has great application potential in targeted therapy, fluorescence labeling and magnetic fluid seal and so on.