Abstract: In recent years, polymer-based composites with excellent dielectric properties have recently attracted considerable interest for their potential applications in the field of microelectronics, such as electrostriction for artificial muscles, advanced dielectric capacitors and other portable flexible electronics. The combination of ceramic and conductive particles selected for the filler system has been proved to be an effective strategy to improve the dielectric properties of the polymers. The co-existence of the inorganic ceramic and conductive fillers could simultaneously contribute to the relatively higher dielectric constant and lower loss. Therefore, in this work, benefitting from the interaction between carbopol (CP) and hydroxylated barium titanate (hBT) nanoparticles, hBT surface can be coated by CP. Consequently, a core-shell structured nanoparticle was fabricated by surface modification of hBT with CP and named CP@hBT. Subsequently, the CP@hBT nanoparticle was used as the ceramic filler and the amino functionalized multiwalled nanotubes (CNT) was used as the conductive filler, polydimethylsiloxane (PDMS) as the matrix, respectively. Then, CP@hBT-CNT/PDMS dielectric composites were successfully prepared by solution blending. In this work, the effect of surface modification of hBT with CP on the microstructure and the dielectric properties of CP@hBT-CNT/PDMS were systematically studied. The results indicated that the sedimentation and aggregation of CP@hBT nanoparticles can be effectively prevented after the functionalized modification of hBT by CP, thereby leading to enhance dispersion of CP@hBT nanoparticles in PDMS matrix. As a result, with a CNT loading of 0.75% (mass fraction), the CP@hBT-CNT/PDMS composite exhibited a high dielectric constant value of 138 and low dielectric loss(<0.5) at 1 000 Hz.