Abstract: Polyaniline deposited BaTiO3 hybrid nanoparticles (BT@PANI) were synthesized via in-situ polymerization process and then used as fillers to fabricate the BT@PANI/epoxy composites. The dielectric constant of the composites increased with the increment of PANI in BT@PANI(while the fraction of BT decreased in the composite), which was attributed to the enhanced interfacial polarization induced by the conducting PANI. The value of k increased from 17 for 0 wt% PANI to 53 for 26 wt% PANI. No typical percolation effect was observed in the composite and when the content of PANI in the BT@PANIreached 26 wt%, the conductivity maintained a low value of 1.64×10－6 S/m. Besides, the dielectric constant of the composites jumped remarkably inthe measured temperature range from 60℃ to 100℃ as anevidenceof the stronger interfacial polarization generated by conducting PANI with temperature increasing, theenhanced motion of epoxy molecule chains around Tg (90℃)and the phase transition of BT near the curie point 120℃.