The effects of thermal treatment of polycrystalline ZnO–TiO2 systems on their luminescence emission and phase properties were investigated using ex situ cathodoluminescence and backscattering electron microscopy. The main features of the spectrum are a blue band at 2.75 eV for the phase of TiO and a complex visible band at 2.18 eV for the phase of ZnO, whose peak intensity depends on the annealing temperature. The spectrum intensity is dominated by the ZnO phase when annealing temperature was 720°C, which is attributed to abnormal grain growth. Competition is observed between the broad band peaked at 2.18 eV and visible band peaked at 2.75 eV as the annealing temperature changed (820°C-920°C). The cathodoluminescence density is gradually governed by the TiO2 phase, and the emission in polychromatic and monochromatic imaging is stronger equally at 920°C. The nucleation of the TiO2 and ZnO grains is present in the backscattering electron images as well.