For present ceramic particles/polymer dielectric composite materials, their dielectric properties and thermal conductivity haven't met the application requirement at the same time. In this research, to achieve this goal, barium titanate@super short MWCNTs (BT@SSCNT) core-shell particle was prepared in a confinement reactive space built by water phase and oil phase. Polyvinylidene fluoride (PVDF) based composite flexible films reinforced by the BT@SSCNT particles possessed desired dielectric and excellent thermal behaviors. Especially for the composite film with 60 wt% (containing less than 17 wt% SSCNT) loading, at 102 Hz and in the wide temperature range of −40–140 °C, dielectric constant and dielectric loss varied from 476 to 764 and from 2.74 to 4.58, respectively. Meanwhile the thermal conductivity of this film reaches 25.43 W/(m K). The promising dielectric properties and high thermal conductivity of the films are attributed to multiple roles of SSCNT shell layer including external electric field applying on BT particles, tremendous interfacial polarization area, restricted electron motion and electron efficient in transporting heat. The BT@SSCNT/PVDF composite films can be a promising candidate for the modern electronic industry. © 2020