Abstract: The urchin ZnO nanostructure were obtained by a simple hydrothermal reaction of Zn（AC）2 with NH₃ and NaBH₄ at 140℃ for 2 h.The products were characterized by X-ray diffraction,scanning electron microscopy and transmissom electron microscopy.The results showed that the urchin ZnO nanostructure with the diameters of 3~17μm are assembled from one-dimensional nanorods with the diameter and length of 100 nm and 500 nm~3μm.Possible growth mechanism of the urchin ZnO nanostructure were proposed.NaBH₄ may react with a small amount of H+ in the reaction system,Lots of microbubbles of H₂ produced.Small ZnO nanodots may aggregate around the gas–liquid interface between H₂ and water to form hollow ZnO nanodot-based microspheres,The constituent ZnO nanodots will evolve into ZnO nanorods along the direction by oriented attachment to obtain the urchin ZnO nanostructure.Photocatalytic activities of the urchin ZnO nanostructure and ZnO nanorods in the degradation of methyl orange were investigated.The degradation rate of the urchin ZnO nanostructure and ZnO nanorods under 70 min UV irradiation,were 97% and 67%,respectively.