Copper oxide was prepared via the calcination of copper oxalate precursor. By using high-temperature solvent method, the precursor decomposed under nitrogen atmosphere and copper nanoparticles were obtained. The microstructure and properties of the products were characterized by scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy and other analysis methods. The results show that the obtained copper oxide is constructed by nanoparticles. The sample is porous and has a good catalytic activity. Three copper samples were obtained by controlling the reaction time. The particle size of the samples was calculated to be about 44.3 nm, 17.1 nm and 9.9 nm respectively.