We report on the synthesis of polycrystalline thin films of PbZr0.3Ti0.7O3 (PZT) by the so-called chemical solution deposition technique. The thin films were deposited on Pt/Ti/SiO2/Si substrates by the spin-coating method, and were heat treateded at 700 °C in air and under several oxygen pressures (10≪PO2≪60 bars). The structural, morphological, and ferroelectric properties were characterized by x-ray diffraction (XRD), infrared and Raman spectroscopy, atomic force microscopy (AFM), and polarization-electric-field hysteresis loop measurements. The XRD and the Raman spectroscopy results revealed that the films heat treated in air and at low oxygen pressures (PO2≪40 bars) are single phase. However, analysis of the data indicated a clear decreasing of the crystallization degree of the films with increasing oxygen pressure. AFM results showed the PZT films display a rosette structure embedded in a matrix, which comprises grains with an average grain size ranging from 60 to 120 nm. Ferroelectric hysteresis loops’ measurements performed on these PZT films exhibited a clear decrease of the remnant polarization with increasing oxygen-pressure PO2. This study indicated some important- effects of the high oxygen-pressure annealing on the physical properties of PZT thin films.