A dense and thick lead zirconate titanate (PZT) epitaxial film was synthesized on a Ba(Ti-0.9,Zr-0.1)O-3 (BZT) substrate via hydrothermal treatment. The PZT films showed an excellent in-plane alignment with the BZT substrate, and also the crystallinity of the films was strongly dependant on the hydrothermal synthesis condition. An epitaxial PZT film as thick as 4.6 microns could be obtained after three-time repetition of the hydrothermal treatment.