Pb(Zr0.48Ti0.52)O-3 thin films at 20% excess Pb were synthesized on Pt/Ti/SiO2/Si(100) substrates at different annealing temperatures by a metal-organic decomposition process. The microstructure of the PZT films was investigated by x-ray diffraction and atomic force microscopy. The composition of the films was characterized by Rutherford Backscattering Spectroscopy (RBS). These results showed that The PZT films have perovskite phase coexisted with PbO2 phase. The PbO2 phase mainly was formed by excess Pb which congregate at boundaries of crystalline grains during the annealing process and may be absorbed part of oxygen ion at normal sites, thus leading to an increase of oxygen vacancies in the PZT film. PbO2 phase and oxygen vacancies act as pinning centres, which has an effect on the ferroelectric domain switching. This eventually resulted in an increase of fatigue rate in PZT films.