The (Ca0.97Ba0.03)Cu3Ti4-xNbxO12(x=0, 0.01, 0.03, 0.05, 0.07, 0.10, 0.15, 0.20) ceramics have been prepared by the solid state reaction method. The influences of the mole fraction of Nb5+ on the phase structure and surface micromorphology of (Ca0.97Ba0.03)Cu3Ti4O12 ceramics have been investigated using the X-ray diffractometer and scanning electron microscope. The variations of the electric properties of the (Ca0.97Ba0.03)Cu3Ti4-xNbxO12 ceramics are obtained by the high and low temperature dielectric performance test system and impedance tester. The results show that the (Ca0.97Ba0.03)Cu3Ti4-xNbxO12 ceramics of various components are single-phase cubic perovskite structure. With the increase of the mole fraction of Nb5+, the grain growth of (Ca0.97Ba0.03)Cu3Ti4-xNbxO12 ceramics can be inhibited effectively and the abnormal grain growth is eliminated. The grain boundary resistance of (Ca0.97Ba0.03)Cu3Ti4-xNbxO12 ceramics can be effectively increased by appropriately doping Nb5+, thus its dielectric loss can be reduced, and the temperature stability of the relative dielectric constant of (Ca0.97Ba0.03)Cu3Ti4-xNbxO12 ceramics can also be improved.