Transparent zinc oxide (ZnO) films were prepared on ZnWO4 crystal by sol-gel technique. Surface morphology of ZnO films were observed with optical mi croscope. The results of show that ZnO films are formed in three different stage s from nucleation on surface, grain growth to island formation. Because ZnO crys tal nucleus were grown under non_equilibrium condition, it is inevitable that de ndrite growth, fractal growth and spinodal decomposition phenomenon are involved in the growing process.