To improve the dielectric performance of high-dielectric-constant conductive filler/polymer composites, polyaniline was deposited on exfoliated graphite nanoplates (xGNPs) by in-situ polymerization method to form polyaniline (PANI) coated xGNPs (xGNPs@PANI) as the conductive filler for the oxidized styrene-butadienestyrene copolymer (SBS-FH) containing both hydroxyl and formyloxy groups. The results of TEM, SEM, FTIR, TGA, Raman spectrum, XPS, and WAXD showed that PANI had been coated onto the surface of xGNPs successfully. The xGNPs@PANI/SBS-FH composites were prepared by a simple solution blending method and the homogenous distribution of xGNPs@PANI in the SBS-FH matrix was confirmed by SEM. The presence of xGNPs@PANI was found to significantly improve the dielectric properties of resultant composite compared to the unmodified xGNPs. For example, the xGNPs@PANI/SBS-FH composite near percolation threshold filled with 9.38 vol.% xGNPs@PANI showed a dielectric constant of 56.8 and a dielectric loss factor of 0.51 at 1000 Hz, while the corresponding values of xGNPs (1.19 vol.%)/SBS composite were 15.96 and 2.91 at 1000 Hz, respectively. In addition, the incorporation of xGNPs@PANI into SBS-FH could effectively enhance the thermal conductivity of resultant xGNPs@PANI/SBS-FH composite. (C) 2018 Elsevier B.V. All rights reserved.