Polar surface dominated ZnO brush-like nanostructures have been successfully synthesized on Si substrates via a carbon-thermal reduction method at a temperature of 900 degrees C. Specially, the axis of the as-prepared brush-like nanostructures is a straight nanorod along the [0001] direction and enclosed by six {01 (1) over bar0} surfaces, which grew first; the sixfold symmetric nanonails were later formed along the equivalent a axes (<01<(1)over bar>0 >) perpendicular to the central nanorod, and the brush is formed by epitaxial growth of nanonails on the central nanorod. The growth of the structures is based on firstly sprouting of nanorods and then epitaxial growth of nanonails in the six symmetric [01 (1) over bar0] directions. Based on the testing results, the growth mechanism of the ZnO brush-like nanostructures was discussed, emphasizing the self-catalysed of ZnO and the polar orientation of ZnO nanostructures, and the formation of the nanonails may due to the different chances of absorbing the arriving vapors. (C) 2010 Elsevier B.V. All rights reserved.