The measurement of dielectric susceptibility under various frequencies for Pb(Zr0.52Ti0.48)O3 (PZT) ceramics shows that there exists a dielectric loss peak below and close to phase transition temperature, which is relaxational characteristic but disagrees with Arrhenius relation. The peak arise from the interaction between domain walls, lattice and pinning defects. In this paper the behavior of the dielectric loss peak of PZT under various frequencies is simulated by using the dynamic equation of viscous motion of domain walls and by considering the Curie temperature dispersion in ceramics as well. The agreement between the simulatied result and experimental data is quite satisfactory. And from the parameters of simulation the viscous coefficient of the motion of domain walls and the recovering force constant of pinning defects are calculated.