A tensile or compressive mechanical constraint was applied, during annealing, on the Pb(Zr0.6Ti0.4)O-3 (PZT) ferroelectric films to investigate the effects of stress on its crystal structure and electric properties. The external stress was applied by bending the substrate into a circular section. By using both precrystallized film structure and high constraint strain (0.08%), the stress states of PZT during the crystallization process became controllable. Structural change of polycrystalline PZT was observed when crystallized under a compression constraint. Moreover, these films with compression constraint annealing exhibited enhanced remnant polarization by similar to 70% and increased dielectric constant by similar to 68%. The variations in ferroelectric behaviors were correlated to domain configuration, texture, amount of pyrochlore phase, grain size and residual stress, which are dependent on the stress state during annealing process.