Zinc oxide is one of the promising transparent conducting oxide materials because of its interesting physical properties. In this work, ZnO thin films have been prepared by ultrasonic spray pyrolysis technique. Structural properties of the films have been characterized by X-ray diffraction. Transmittance spectra have been taken by UV-VIS spectrophotometer. The films have been found to exhibit high transmittance (approximately 85 %). Optical constants of ZnO film such as refractive index (n) and extinction coefficient (k) have been calculated from the transmittance spectra by using envelope method. Also absorption coefficient (a) and thickness of the film have been calculated using this method. Optical method has been used to determine the band gap value of the film. To investigate the surface properties of the film, atomic force microscope images have been taken.