The invention discloses a dielectric material with an ultra-high dielectric constant and a preparation method thereof. The dielectric material has a chemical formula of BaTi1-xHfxO3, wherein x is no less than 0.03 and no more than 0.15. According to the invention, the dielectric material with the ultra-high dielectric constant is obtained by adopting a traditional preparation method of solid-phase synthesis. The dielectric material provided by the invention has the advantages of simple components and processing steps, operational simplicity and good repeatability, and is mainly applied to the fields like power capacitors, energy storage capacitors and MLCC.