Cobalt hydroxide has been prepared using cobalt nitrate, cobalt carbonate and cobalt sulfate respectively as raw materials. Taking glycol as solvent and reductant, the spherical, monodispersed, ultrafine cobalt powder is prepared. The influence of prophase cobalt hydroxide prepared by different cobalt salts over follow-up reaction is studied, and the affects of quantity of sodium hydroxide and cobalt hydroxide in unit volume of glycol, reaction time, temperature and additives on cobalt particle size and shape are also discussed. The microstructure of ultrafine cobalt powder is studied by SEM and XRD. The results show that the cobalt powder is spherical, the crystal mostly with face centered cubic (fcc) structure, the average particle size is 0.8μm, the cobalt content is 99.5% .