Abstract: This paper reviewed the latest research progress in novel composite dielectrics based on polymers and thermally conductive fillers and analyzed the effects of several novel inorganic nanoparticles and their content, surface modification and processing methods on the thermal conductivity and dielectric properties of the composite dielectrics. These nanoparticles include nanosized diamond, carbide silicone, ferroelectric ceramics and other inorganic functional particles. Moreover, the paper also introduced some types of organic molecular crystals which could improve the thermal conductivity of polymers by constructing a continuous way for phonons. The continuous thermal conduction pathways for phonon transfer could be constructed in the matrix by use of novel inorganic particles and organic molecular crystals, thus leading to the suppression of interfacial thermal resistance and the improvement of thermal conductivity. Compared to the thermally conductive particles used commonly, the novel thermally conductive particles not only can improve the thermal conductivity but also can enhance other physical properties such as magnetism, excellent dielectric properties and energy storage of the composites.