Abstract: Organic ligands are widely applied in preparation of metallic complexes, and in high temperatures, can be burned and eliminted from the coordination sphere, remaining only oxide group. In a reaction between Co(NO₃)₂.6H₂O, ammonium oxalate and F-127 as a surfactant to control the particles size, cobalt-oxalate was formed. After performing Thermal Gravimetric Analysis (TGA) to find the optimum decomposition temperature, the precipitate was calcined and the resulted nano cobalt oxide was characterized by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD). The crystalline pure and nanosized particles had the average size<40 nm.