Abstract: The physical properties of metamaterials with negative parameters and the negative permittivity behavior of the intrinsic properties of materials deserves further investigation, the systematic study of the influence of chemical composition on their permittivity behavior, and the investigation of the realization and regulation mecha-nism of negative permittivity behavior. The carbon fiber/alumina (CF/Al₂O₃) ceramic composites were prepared by hot-press sintering, and the effects of different CF content on the micromorphology and electrical properties of composites were studied. By adjusting the CF content in the composites, the negative dielectric behavior was rea-lized in the frequency range of 1 kHz-10 MHz, and the conductive mechanism changed from hopping conduction to metal-like conductivity. It is found that the increased CF forms three-dimensional interconnection network in the composites, and the negative permittivity is caused by the plasma oscillation of the internal free electrons in the CF network. With the increase of CF content, the absolute value of negative permittivity becomes larger, and the dispersion characteristics of permittivity conforms to the Drude model.