Owing to the rapid development of capacitor for terahertz (1 THz=1012 Hz) electronics, the THz dielectric properties of different granular CaCu3Ti4O12 (CCTO) ceramics are investigated experimentally. It is found that the dielectric constant ε r of CCTO of small particles (Φ＜2 μm) is below 700, while exceeds 2000 for larger granular (Φ >10 μm) CCTO in the frequency range below 1 MHz. Correspondingly, the dielectric loss of CCTO is from 0.1 to 0.6. In THz frequency range, however, different granular CCTO ceramics exhibts the same value of εr ( εr =72±3). The ionic polarizability dominates εr , so that it is insensitive to the grain-size of CCTO. However, the larger grain- size increases the scattering cross- section, which enlargers the total extinction ratio of transmission so as to increase the dielectric loss in THz frequency range. It is found that the small granular CCTO is a potential dielectric materials for the application of THz capacitors.