Octahedral Cu 31 S 16 was synthesized by one-step reaction between Cu 2 O octahedra and thiourea solution under ultrasonic irradiation. Cu 2 O octahedra acted as both the precursor and template for the preparation of octahedral Cu 31 S 16 . This method has the advantages of the simplicity and low cost. The Cu 31 S 16 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 Cu 31 S 16 was evaluated. About 99% of the methyl orange was degraded after 60min.