We synthesized ZnO nanocrystal colloids adopting sol-gel method using zinc acetate dehydrate as precursor, and prepared ZnO films on glass substrates by a spin-coating technique. The effect of annealing temperature on the structure, optical and electrical properties has been studied. The crystallinity and morphologies were improved by the annealing. All film samples show high transmittance of above 80% in the wavelength ranging from 400nm to 1000nm. A minimum resistivity of 5.5x10(-3) Omega(.)cm was obtained for the film annealed at 500degreesC. The crystallinity, oxygen vacancies, and nanocrystalline boundaries seems likely to be crucial factors for these properties.