In this paper, zinc oxide (ZnO) colloidal spheres structures were prepared by sol-gel method which is simple, effective and less costly. The scanning electron microscopy (SEM) images illustrated the ZnO colloidal spheres structures with diameter size ranging between 200–700 nm. The particle size distribution of colloidal spheres was determined by the added amount of supernatant in dehydration process. 3 mL and 6 mL of added supernatant were resulted particle size distribution dominant in the range of 250–400 nm and 150–250 nm, respectively. Transmission spectra demonstrated the photonic band gap (PBG) of colloidal spheres prepared with different amounts of colloidal suspension coating sample were near ultraviolet and violet region. The thermal annealing process was introduced to narrow the PBG width of colloidal spheres based on Bragg’s law. Current-voltage measurement of ZnO colloidal spheres based thin film with particles size in the range of 150–250 nm showed that the resistivity of the thin film is 4.5 x 106 Ωcm.