Variations of remanent polarization and coercive field of undoped and yttrium doped Pb(Zr0.65Ti0.35)O3thin films prepared by Sol-Gel processing were observed using hysteresis measurement according to the cumulative switching cycles. Remanent polarization and coercive field of undoped Pb(Zr0.65Ti0.35)O3thin films after 1010polarization reversals were decreased and increased, respectively. But the variations of remanent polarization and coercive field of yttrium doped specimens with the polarization switching cycles were different from those of undoped specimens. In the case of yttrium doped specimens, remanent polarizations were not decreased and coercive fields were increased more than those of undoped specimens after fatigue. It was well known that doped yttrium reduced holes and increased vacancies in PZT thin films. This strongly suggests that the variations of holes and vacancies influence on the remanent polarizations and the coercive fields of Pb(Zr0.65Ti0.35)O3thin films after fatigue. Also, switching time was reduced as the yttrium doping increased.