High-k composites have been actively pursued in the past few years for potential applications in embedded capacitors and energy-storage devices. In this study, Ag@TiO₂ core@shell particles were synthesized by a hydrolysis from titanate alkoxides at room temperature. Composites filled with the particle fillers were characterized for I/V, dielectric and energy-storage characteristics. Mechanisms of influences of Ag@TiO₂ fillers on dielectric properties of composites were investigated. Scanning electron microscopy and energy dispersive spectra exhibit that the synthesized Ag@TiO₂ particles have spherical and fully-coated core@shell structures. X-ray diffraction pattern confirms the phase of Ag and TiO₂ in the particles. The polydimethylsiloxane composites filled with Ag@TiO₂ fillers exhibit a small leakage current of 10 ^-8A/cm ², a high dielectric permittivity of 108, and a very low dielectric loss of 0.2%, and a large energy storage density of 8.58×10 ^-3J/cm ³. Theoretical model containing effective medium theory (EMT) and Maxwell theory were used to compare with experimental results, and interfacial polarizations were proposed to enhance the permittivities of the composites. The composites filled with Ag@TiO₂ fillers show potential applications in the embedded capacitors.