Abstract: The effects of lattice distortion and structural defects of the polycrystalline film have been taken into consideration. A polycrystalline model of ZnO piezoelectric thin film has been established to calculate the SAW velocities and effective electromechanical coupling factors of ZnO-glass and ZnO-fused quartz structure. The calculated values of the polycrystalline model fit the experimental values better than that of simple crystal model. The analysis based on the polycrystalline model also show that the standard deviation of C-axis orientation has only minor influence on the SAW properties of ZnO piezoelectric film and the lattice distortion is the prime detrimental factor.