Polarization and dielectric behavior of Li and Ti co-doped NiO (LTNO) ceramics was investigated. Analysis of the ceramic microstructure and composition indicate that an obvious grain boundary was formed and surrounded the grains, and Ti ions distributed in grains and grain boundaries. The concentration of Ti had a remarkable effect on the dielectric properties of the LTNO ceramics. Positron annihilation spectra measurements implied that a large amount of defects exist in the LTNO ceramic samples. Anomaly polarization-electric field hysteresis loops were observed in the high-permittivity dielectric LTNO ceramics, which are totally different from those for ferroelectric materials and are due to defect-dipoles induced, and electrical conduction effects of samples could also have an influence on the hysteresis loops. The high dielectric constant response of the LTNO ceramics is enhanced partially by the boundary layer capacitor mechanism, and partially by the huge polarization of a large amount of defect dipoles.