The size and morphology of cobalt oxalate powders are the keys to metal cobalt powder production. Spheroidic and fine cobalt oxalate powders were prepared by conventional precipitation when a pulsed electromagnetic field (PEMF) was introduced. The phase structures of the produces were characterized by means of X-ray powder diffraction (XRD). Scanning electron microscopy (SEM) images were used to observe the morphologies of the cobalt oxalate powders. Thermal analyses were performed using TG-DSC thermogravimetric analyzer. Meanwhile, a possible mechanism was proposed based on the interaction between pulsed electromagnetic field and cobalt oxalate cluster. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.