The influence of rapid cooling on the morphology and structures of CuO nanostructures synthesized via oxidation process was investigated. Two suggested approaches were used in this study. First and second oxidation approaches of Cu foil were conducted with single zone tube furnace and muffle furnace respectively. The copper oxide product was characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform –infrared spectrometer (FTIR), ultra violate- visible (UV-VIS) spectrophotometer. XRD patterns showed that there are two copper oxide phases of Cu2O and CuO always coexists and their intensity proportion varying with oxidation temperatures. These results were confirmed by SEM and FTIR analysis. High energy band gap about 3.6eV was calculated at different temperatures for copper oxide nanostructure.