Synthesis, Characterization and Dielectric Properties of pure and Gd doped CaCu3Ti4O12 (CCTO) were investigated. The X-ray diffraction analysis showed single phase, without any impurity phase. The dielectric property of pure and Gd doped CCTO is exhibit an enormously large low-frequency dielectric permittivity ( is of the order of 104~105). This dielectric feature makes some of them promising for the applications in various microelectronic devices.