The dielectric and varistor properties of MgTiO3-CaCu3Ti4O12 composite were investigated in term of a new composite with high dielectric permittivity and breakdown voltage. The MgTiO3-CaCu3Ti4O12 composite ceramics were prepared by a traditional solid-state method. Analysis of microstructure indicated that MgTiO3 addition can refine the grain size. Impedance spectroscopy results showed that the dielectric constant and loss of the composites were stable with the frequency and temperature. The activation energy calculated by the variation of electrical modulus was almost same (0.12 eV) as previously reported one. Especially, the breakdown voltage of the composite ceramics can by adjusted from 200 to 1200 V/mm by controlling the ratio of the amount of CCTO and MgTiO3 composites.