Transition metal oxide micro-/nanostructures demonstrate high potential applications in energy storage devices. Here, we report a facile synthesis of highly homogeneous oxide composites with porous structure via a coordination polymer precursor, which was prepared with the assistance of tartaric acid.The typical product, Fe-Mn-O composite was demonstrated here. The obtained Fe-Mn-O product was systemically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, elemental mapping analysis, and X-ray photoelectron spectroscopy. It was demonstrated that the Fe-Mn-O nanocomposite shows interconnected porous structure, in which iron,manganese, and oxygen are uniformly distributed. In addition, the Fe-Mn-O nanocomposite was then fabricated as capacitor electrodes. Operating in an aqueous neutral solution, the Fe-Mn-O composite electrodes showed an wide working potential window from 0.2 to 1.0 V(vs. SCE), and a specific capacitance of 86.7 Fg~(-1)or 0.4 Fcm~(-2)at a constant current density of 1 Ag~(-1)with good cycle life. This study offers a new precursor approach to prepare porous metal oxide composites, which would be applied in energy-storage/conversion devices, catalysts, sensors, and so on. Transition metal oxide micro- / nanostructures demonstrates high potential applications in energy storage devices. Here, we report a facile synthesis of highly homogeneous oxide composites with porous structure via a coordination polymer precursor, which was prepared with the assistance of tartaric acid. The typical product , Fe-Mn-O composite was demonstrated here. The obtained Fe-Mn-O product was systemically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, elemental mapping analysis, and X-ray photoelectron spectroscopy. demonstrated that the Fe-Mn-O nanocomposite shows interconnected porous structures, in which iron, manganese, and oxygen are uniformly distributed. In addition, the Fe-Mn-O nanocomposite was then fabricated as capacitor electrodes. the Fe-Mn-O composite electrodes showed an extensive working potential window from 0.2 to 1.0 V (vs. SCE), and a specific capacitance of 86.7 Fg ~ (-1) or 0.4 Fcm ~ (-2) at a constant current density of 1 Ag ~ (-1) with good cycle life. This study offers a new precursor approach to prepare porous metal oxide composites, which would be applied in energy-storage / conversion devices, catalysts, sensors, and so on.