In order to conciliate dielectric and non-Ohmic properties of CaCu3Ti4O12 (CCTO) ceramics, NiO, SnO2, SiO2, and Al2O3 were added as sintering aids to promote the grain growth of CCTO ceramics. Microstructure, dielectric properties, and non-Ohmic behavior of the CCTO ceramics were investigated. Among them, NiO-modified CCTO exhibits good dielectric and non-Ohmic properties (epsilon = 69833, tan delta = 0.073, alpha = 3.66 and E (B) = 296.7 V/cm), due to NiO is also one of giant dielectric materials. Therefore, it is suitable for applying semiconductor circuits. The relationship between electrical current density (J) and electrical field (E) demonstrated that Schottky barrier should exist at grain boundaries. Non-linear coefficient alpha was directly proportional to the height of barrier. Depressing barrier width would improve significantly dielectric permittivity but decrease breakdown voltage.