Urchin-like Co3O4 hierarchical micro/nanostructures have been successfully synthesized by calcining urchin-like precursor CoCO3, which are prepared by a facile hydrothermal route. The particle size of the urchin-like Co3O4 could be easily controlled by altering the calcination temperature. The morphology and structure of the as-prepared urchin-like products were characterized by XRD, FESEM and TEM. Photocatalytic measurement demonstrates that these urchin-like Co3O4 micro/nanostructures show good photocatalytic effect and their degradation efficiency is strongly dependent on their particle size. Furthermore, a plausible reaction mechanism is also proposed to illustrate the photocatalytic processes of Co3O4. (C) 2011 Elsevier B. V. All rights reserved.