Pure CaCu3Ti4O12 was successfully prepared by a glycine-nitrate process using a relatively low calcination temperature and short reaction time of 760 degrees C for 4h. Fine-grained CaCu3Ti4O12 ceramics with dense microstructure and small grain size were obtained after sintering for 1h. The nonlinear coefficient of a fine-grained CaCu3Ti4O12 ceramic calculated in the range 1-10mA/cm2 was found to be very high of similar to 16.39 with high breakdown electric field strength of 1.46x104V/cm. This fine-grained CaCu3Ti4O12 ceramic also exhibited a very low loss tangent of 0.017 at 20 degrees C with temperature stability over the range -55 degrees C to 85 degrees C. The grain growth rate of the CaCu3Ti4O12 ceramics was found to be very fast after increasing the sintering time from 1.5 to 3h, leading to formation of a coarse-grained CaCu3Ti4O12 ceramic with grain size of about 100-200m. The dielectric permittivity of this coarse-grained ceramic was found to be as high as 1.03x105 with a low loss tangent of 0.054.