In recent times, there have been increasingly researches on the dielectric properties of carbon-based composites, and its dielectric tunability is a scorching analysis subject. On this paper, epoxy resin/carbon fiber/phenolic residual carbon (EP/CF/C) was ready by high-temperature sintering, vacuum liquid section impregnation and hot-press curing strategies. The AC conduction conduct, dielectric properties and impedance properties of composites with totally different CF/C compression ratios (1, 1.5, 2) are studied. With the rise of CF/C compression ratio, the unfavorable dielectric properties of composites are getting stronger and stronger. The outcomes present that when the CF/C compression ratio is 1, the composites happen percolation phenomenon and dielectric fixed is unfavorable. When the CF/C compression ratio is 2, absolutely the worth of the unfavorable dielectric coefficient of the EP/CF/C composite reaches 9.8 × 104, and the conductivity reaches 0.54 S/cm. As well as, impedance evaluation has additional confirmed that the inductance properties result in the unfavorable dielectric properties of the fabric. The adjustable unfavorable dielectric properties of EP/CF/C composites can present some options for the sector of electromagnetic shielding and capacitors.