Three kinds of tetrapod-like ZnO nanostructures have been synthesized simultaneously in different regions of the same preparation apparatus by rapidly heating zinc powder, in which two kinds of novel tetrapod-like ZnO nanocrystals with hexagonal needled arms and pyramid tip arms were first reported. Oxygen concentration is deemed as the critical experimental parameter for the formation of different morphologies of ZnO nanostructures. EDS and PL measurements show that the ZnO nanocrystals with hexagonal cylinder arms and pyramid tip arms have high stoichiometric proportions and good crystal qualities, while the ZnO nanocrystal with hexagonal needled arms has a low stoichiometric proportion and relatively poor crystal quality. Annealing in oxygen ambient can improves the crystal quality of the ZnO nanocrystal, while annealing in air and vacuum ambient, deteriorates its crystalline quality (C) 2004 Elsevier B.V. All rights reserved.