Abstract: To improve the dielectric properties of dielectric material, an in-situ polymerization method was used for preparing the combined functional filler BT/PANI, and three-phase composite BT/PANI/PVDF was prepared using BT-PANI as the functional phase. The structure of BT/PANI was characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD). The morphology and dielectric properties of the three-phase BT/PANI/PVDF were characterized by scanning electron microscopy (SEM) and impedance analyzer. The polarization modes of the BT/PANI/PVDF system were analyzed, and the variations of dielectric properties with frequency were explained based on it. Results show that the functional phase BT/PANI is uniformly coated by polymer matrix in BT/PANI/PVDF to obtain good dielectric properties.