Carbon coated nano Co particles were prepared by pyrolysis of Co-exchanged resin (Co/D113) at 400 to 700 ℃. The TG results show that the thermal stability of Co/D113 is better than that of pure D113 resin. The XRD and TEM results reveal that the cobalt particles existed mainly in the form of fcc Co phase, and the particle size of nano-Co increase with the increase of pyrolytic temperature. The magnetic tests show that the coercivity(Hc) of the pyrolyzates obtained at 400 to 700 ℃ at room temperature are much higher than that of the corresponding bulk material, and the Hc value is influenced by the size of the nano particles. The saturation magnetizations (Ms) of all the pyrolyzates are lower than that of bulk material and increase with the increase of pyrolytic temperature