Lanthanum-modified lead zirconate titanate (PLZT) thin films, with the La/Zr/Ti ratio being 9/63/37, were deposited on indium tin oxide (ITO)-coated glass substrate by R.F. magnetron sputtering method. Effects of heat-treatment conditions on the structure and chemical homogeneity of the PLZT thin films were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The PLZT thin films with desired perovskite structure were obtained after covered with lead oxide and then annealed at 625℃ for 150 min. The binding energy of Pb4f7/2, Ti2p3/2, Zr3d5/2, La3d5/2, and O1s in PLZT thin films were: 138.3, 455.7, 181.2, 835.9, and 529.4 eV, respectively. The excess lead oxide in the PLZT thin films promoted the perovskite structure formation, and baffled the movement of TiO2 and ZrO2 as well. A small quatity of TiO2 and ZrO2 coexisted with PLZT in the surface of samples. And the lack of oxygen inside the films resulted in the valence decrease of a little part of Ti's from +4 to +2.