We have studied on hydro-thermally synthesis of Pb(Ti, Zr)O3(PZT)piezoelectric polycrystalline thick film on titanium (Ti) substrate. The purpose of this study is resolving the problems for application of PZT hydrothermal polycrystalline thick film to the ultra miniature high frequency medical ultrasound array probe. The problems were the existence of pinholes in the deposited PZT film, the rough surface of that, low dielectric breakdown electric field etc. The surface of Ti substrate was pretreated to have hydrophilic property by using high reactivity of hydrogen peroxide for resolving the problems in this study. As results, hydrophilic property on the surface of Ti substrate was improved. Surface of PZT hydrothermal polycrystalline thick film without pinholes and smooth surface of that were obtained. Furthermore, the material properties like density, Young's modulus and piezoelectric constant d
31 were increased by the pretreatment of Ti substrate. Consequently, dielectric breakdown electric field of PZT hydrothermal polycrystalline film was improved.