The oriented La modified PZT thin films were prepared on Pt/Ti/SiO2/Si substrate by the LB technique. The pre-sintering temperatures and the annealing temperatures for La modified PZT were determined by TG-DTA curves and XRD detect results. XRD detection of PZT and PZT with different La amount illustrated the crystal constructions and the effects by modification. The AFM observation of PLZT thin films with organic acid indicated that the LB technique could obtain smooth and flat film with the deposition of PLZT particles within nanometers on substrate. The detection results of the electrical properties indicated that the modification of La had great influence on the electric properties of LB thin film. PLZT thin film by annealing at 650°C had better dielectric constant of 569.2 and dielectric loss of 0.4915 at 5 kHz. And the amount of La of 2% in mass gave the piezoelectric constant of 14pC/N.