Zinc oxide (ZnO) is an emerging optoelectronic material in large area electronic applications due to its various functional behaviors. We report on the fabrication and the characterization of ZnO nanorods. The ZnO nanorods were synthesized using sol-gel hydrothermal technique on oxidized silicon substrates. Different annealing temperatures were explored in the sol-gel hydrothermal synthesis of the ZnO nanorods. In order to investigate the structural properties, the ZnO nanorods were measured using X-ray diffractometer (XRD). The optical properties were measured using ultraviolet-visible (UV-Vis) spectroscopy. The influence of the annealing treatment on the structural and optical properties of the ZnO nanorods will be revealed and discussed in this paper.