In this work, we studied the effect of annealing temperature on the structural, morphological, and optical properties of copper oxide thin films that were prepared by the sol-gel method and deposited on glass substrates using the spin coating technique in order to improve their properties and use them in the optoelctronic field. The XRD results showed that all samples It is polycrystalline and has a monoclinic crystal structure. The results of the SEM device and the UV-VISIBL device also showed that the film that was annealed at a temperature of 450 °C gave the best results in terms of a homogeneous layer with less void space and pores and a low grain size compared to other films, as well as high absorption in the visible region. The optical band gap decreased from 3.64 to 2.75 eV due to the improvement of crystallization and the increase in crystal size by increasing the annealing temperature to 450 °C.