Ultralong ZnO nanocombs have been synthesized on silicon substrates with a high growth rate of ~7 μm/s using a simple "thermal evaporation and condensation" method promoted by Cu catalysts. The lengths of the ZnO nanocombs range from several millimeters to more than one centimeter and the diameters of the branches are about 300 nm. The growth mechanism of the ultralong nanocombs and the catalytic behavior of the copper are discussed. The nanocombs were readily separated and their applications as optical polarizer and grating were investigated. The results show that the ultralong ZnO nanocombs can act as effective optical components in miniaturized integrated optics systems.