Abstract: Preferred orientation of ZnO thin films deposited by sol-gel deposition technique could be manipulated by changing annealing temperature. In this study, we used spin coating method to coat glass slides with sol-gel ZnO thin films, composed of zinc acetate dihydrate Monoethanolamine (MEA), de-ionized water and isopropanol. The effect of the annealing temperature on the structural properties of these films is investigated. These ZnO thin films were preheated at 275°C for 10 min and annealed either at 350, 450 or 550°C for 80 min. After heat treatment, each sample was taken out for ex situ Atomic Force Microscopy (AFM) measurements to study the surface morphology. Fractal analysis has been applied to describe the surface morphology and extracting structural parameters of thin films. Thin films also were characterized by X-ray Diffractometery (XRD) method. XRD analysis revealed that the annealed ZnO thin films consist of single phase ZnO with wurtzite structure (JCPDS 36-1451) and show the c-axis grain orientation. Increasing annealing temperature increased the crystallite size and the c-axis orientation of the film after 450°C. It was found that there was a significant effect of annealing temperature on the structural parameters of the film such as roughness exponent, fractal dimension and strain along the c-axis.