This paper is concerned with Cu-doped nano-crystal ZnO thin films deposited on Si (1 0 0) substrates and prepared by sol–gel method. The analyses of these thin film samples with X-ray diffraction (XRD) and scanning electron microscopy (SEM) reveal that these thin films have polycrystalline wurtzite structures and high c-axis preferred orientation. The photoluminescence (PL) spectra of thin film samples at room temperature show that these thin films have strong emission near ultraviolet (UV) and weak defect-related deep level emission in visible regions. These thin film samples have high UV-to-visible emission ratio (about 13–15). In addition, the influence of Cu-doped concentration and annealing condition upon the structural and optical properties of these samples are also discussed in this paper.