Sol-gel processed PLZT thin films were fabricated on ITO-coated glass substrates with RTA (rapid thermal annealing). The electrical and optical properties such as hysteresis curves, dielectric constant, dielectric loss and optical transmittance of thin films were investigated. The PLZT thin films were crystallized to the perovskite structure by RTA at 750 degrees C for 5 min. As the La percentage was increased, the dielectric constant increased, and that of 9/65/35 PLZT thin film was 1750. The coercive field and remnant polarization decreased with La increase from 33.82 kV/cm to 14.71 kV/cm and from 39.26 mu C/cm(2) to 9.57 mu C/cm(2) respectively. As the Zr percentage increased at 2% La, the coercive field decreased from 52.94 kV/cm to 30 kV/cm, but the remnant polarization increased from 22.74 mu C/cm(2) to 50.75 mu C/cm(2), and the dielectric constant had a maximum value of 1269 at 2/55/45 composition. The optical transmittance was increased as La percentage increased but was decreased as the annealing temperature increased.