摘要： Making effective usage of quantum size effect is a foregrounded strategy to design and fabricate excellent electromagnetic microwave absorption materials. In this research, ZnFe2O4 quantum dots were coated by hybrid amorphous carbon to form a sea islands structure by a facile electrostatic self-assembly synthetic technology. Simultaneously, the rejection of heterogeneous charges leads to the formation of quantum dots, by which the quantum size effects on dielectric and magnetic characteristic were investigated. Consequently, multiple hetero-interface and interfacial polarization was originated from polycrystalline feature of ZnFe2O4 with spinel and inverse spinel structures. In particular, the electromagnetic microwave absorption properties of ZnFe2O4 were greatly optimized, as the minimized reflection loss reached -40.68 dB at the frequency 11.44 GHz and thickness 2.5 mm, while the effective bandwidth corresponding was 3.66 GHz (from 9.87 to 13.52 GHz). The largest effective bandwidth was 4.16 GHz (from 8.08 to 12.24GHz) with a thickness of 3 mm. It is suggested that high performance of microwave absorption of ZnFe2O4 quantum dots was well guided by the optimized impedance matching and attenuation constants.