High quality ZnO films on alpha-Al2O3 (sapphire) have a great important application for optoelectronic devices in the future. This study investigated the influence of electric field on the atomic layer epitaxy of ZnO on the (0001) sapphire substrates. Theoretical analyses indicated that the polarization orientation and the polarization forces were the two effects that might influence the ZnO epitaxial growth. The experimental results indicated, for the first time, that electric field could make remarkable growth difference for the ZnO films with this method. Higher quality of epitaxial films has been obtained with a proper magnitude and gradient of the electric field in the geometry of this study. Comprehensive analyses revealed that electric field-induced increase of the hydroxyl packing density on the substrate surface accounted for the results. This study provides a new resort to grow high quality films by chemical vapor deposition (CVD) methods.