The nanosized anode material Co 3 O 4 for lithium ion rechargeable batteries was synthesized through pyrolysis of the oxalate precursor, which was prepared with rheological phase reaction from cobaltous hydroxide carbonate and oxalic acid. The Co 3 O 4 samples were characterized by X-ray powder diffraction, transmission electron microscopy and electrochemical testing. The results revealed that the samples exhibited large lithium storage capacities and the reversible capacities are more than 900mAh.g - 1 . The influence of particle size of Co 3 O 4 on the capacity and cycle-ability was discussed. The sample showed the best electrochemical property with the average particle size of about 37nm.