0.1M of CuCl2.2H2O dissolved in double distilled water as a starting solution was used to spray on glass substrate. After preparing CuO thin film, we used UV-Visible spectrophotometer to recording the absorption spectra. From these spectra, it can calculate some of optical constants. The absorption, absorption coefficient, and extinction coefficient increase with increasing annealing temperature. While the skin depth and energy gap decreases with increasing annealing temperature.