Poly(vinylidene fluoride) (PVDF) based nano dielectric composites have been investigated widely due to their potential application in sensors, actuators, and energy storage fields. To achieve these goals, a novel modification of PVDF electroactive films was prepared due to the exfoliated and oriented Na + -MMT with the assistance of different cationic chain length imidazole-based ionic liquids.The results proved the ion exchange between Na + -MMT and ILs promoted exfoliation and uniform dispersion of Na + -MMT in PVDF matrix efficiently even under a low ILs content (<0.05%). Furthermore, the existence of ILs and shearing force contributed to the oriented dispersion of Na + -MMT. The synergistic effect of Na + -MMT and ILs induced the crystal conformation transition from non-polar α-crystal to electroactive β/γ crystal. The ILs with longer cationic chains behaved much higher inducibility for PVDF electroactive phases. Compared with pure PVDF, PVDF/Na + -MMT/ILs nanocomposites with longer cationic chain ILs showed higher dielectric constant, breakdown strength, and energy density, while kept low-dielectric loss and conductivity. The improved compatibility between PVDF and Na + -MMT due to the ion exchange and decreased crystal size for the polar β/γ crystal enhanced the transparency and elongation at break of PVDF/ Na + -MMT/ILs nanocomposites significantly. The results proved [C16MIM] [Cl] behaved optimum synergistic modification effect for the nanocomposites, and which showed potential applications in dielectric energy storage and microelectronic fields.