The novelty of the work is the theoretical justification and experimental confirmation of the mechanism of interaction of Fe3O4 nanoparticles with Н2О and ovalbumin-OVA, which was carried out with the help of a complex of physical and chemical studies. It was determined that the mechanism is based on the clustero-philicity of nanoparticles and hydrogen, electrostatic and van der Waals interactions. It was established that the interaction of Fe3O4 nanoparticles with OVA took place by the mechanism of static quenching with the formation of an intermolecular non-fluorescent complex that chan¬ges the native structure of OVA. The binding constant varied from 3.3×105 to 4.8×105 L•mol-1 depending on the pH value of the medium and temperature. Thermo¬dy¬namic calculations confirmed the spontaneity of the bin¬ding process with the predominance of the enthalpy factor.