CuFeMnO4 spinel oxide was synthesized by co-precipitation method through calcination of the precipitate precursor at 500-900 A degrees C. The reaction process was investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The structure, valence state and magnetic properties of the powders obtained were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) further. The results revealed that the precipitate is composed of amorphous metal hydroxides and oxides, after which the spinel structure and several phases, such as CuO, Fe3O4 and Mn3O4, turned up in the calcined powders. As the calcining temperature raising, these phases began to transform into a single phase of CuFeMnO4. However, CuO phase segregated from the spinel structure with further calcining. The valence state of Mn ions in octahedral sites and Cu ions in tetrahedral sites were ascertained by XPS, which showed the reduction of Mn4+ and Cu+ during the calcining procedure. Besides, the magnetization of the samples increased obviously with the calcining temperature.