Octahedral Cu31S16 was synthesized by one-step reaction between Cu2O octahedra and thiourea solution under ultrasonic irradiation. Cu2O octahedra acted as both the precursor and template for the preparation of octahedral Cu31S16. This method has the advantages of the simplicity and low cost. The Cu31S16 nanoparticles exhibit a perfect highly ordered, uniform octahedral structure. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), ultraviolet-visible (UV-vis), Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) were used to characterize the products. Additionally, photocatalytic performance of the octahedral Cu31S16 was evaluated. About 99% of the methyl orange was degraded after 60 min. (C) 2012 Elsevier B.V. All rights reserved.