Zinc oxide thin films were prepared by chemical spray pyrolysis technique using Zn(CH

3COO)2 as precursor solution . Structural analyses of the films performed with XRD confirmed that all the films were of zinc oxide having polycrystalline nature with (101).as preferred plane of orientation .A.C. conductivity of zinc oxide thin films measured in the frequency range of 1Hz to 0.1MHz and in the temperature range of 300K to 433K. The experimental studies on a.c. conductivity of ZnO thin films reveal that correlated barrier hopping (CBH) model is the most suitable model to explain the a.c. conduction mechanism in the ZnO thin films. Based on this model, the polaron binding energy (Wm), the height of Coulomb barrier (W) and the characteristic relaxation time (τ0) have been calculated. The values of Wm and W increase as the film thickness decreases, whereas the values of τ0 decrease with decreasing film thickness.