In order to suppress the local electric field distortion caused by the difference of dielectric constant between Barium titanate(BT) nanoparticles and Poly(m-phenyleneisophthalamide)(PMIA), TiO2 and polydopamine(PDA) were coated on surface of BT to generate core-double-shell structured PDA@TiO2@BT nanoparticles(PTBP), then the PTBP nanoparticles were added to PMIA solution to fabricate PTBP/PMIA dielectric composites. The results show that the dielectric constant of PMIA dielectric composite obviously increases with increment of PTBP content. When PTBP content reaches up to 10 wt%, the dielectric constant of PTBP/PMIA dielectric composite increases by 57.1%, compared with that of as-prepared PMIA at 103 Hz. The dielectric properties of PTBP/PMIA dielectric composites also maintain stable at high temperature(>150 ℃). In addition, PTBP nanoparticles significantly improve the energy storage properties of PTBP/PMIA dielectric composites. When the PTBP content is 10 wt%, the energy storage density(Ue) and discharge energy density(Ud) of corresponding PMIA dielectric composite are 1.91 J/cm3 and 1.23 J/cm3 at room temperature and 250 MV/m, respectively, which are 103.2% and 61.8% higher than that of as-prepared PMIA.