Self-assembly three-dimensional (3D) cubic CuO nanostructures with a mean size of approximately 230nm were synthesized by heating cupric acetate (Cu(OAc) 2 ·H 2 O) aqueous solution in the presence of polyvinylpyrrolidone (PVP) and cetyltrimethylammonium bromide (CTAB) under microwave irradiation. The CuO nanostructures were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and thermo gravimetric analysis (TGA), which indicated that the as-synthesized cubic CuO nanostructures were a self-assembly of monodispersed nanoparticles. The concentration of the Cu(OAc) 2 , the molar ratio of Cu(OAc) 2 /NaOH/PVP, together with the heating time by microwave were factors affecting the successful synthesis of cubic CuO nanostructures. The mechanism and the formation factors of the self-assembly were discussed.