Ultrafine　cobalt　powders　have　been　prepared　by　the　freeze-drying　method　and　supported　cobalt　catalysts　have　been　prepared　by　a　new　freeze-drying　immersion　method.　The　results　of　XRD　and　SEM　showed　that　the　precursors　were　amorphous　and　most　were　massive　with　a　size　range　of　2-5　mu　m.　In　the　cobalt　powders　synthesized　by　freeze-drying,　the　grains　were　spherical　in　shape　and　with　sizes　ranging　from　30　to　50　nm.　IR　analysis　showed　that　Co　existed　in　the　precursor　in　the　form　of　[Co(NH3)(x)](2)(C2O4)(3).　EDS　line　scanning　results　indicated　that　catalysts　prepared　by　freeze-drying　could　load　more　cobalt　powders　and　the　distribution　was　more　homogeneous.　Catalyst　activity　was　also　tested　in　the　system　of　carbon　monoxide　oxidation.　The　catalysts　in　this　research　can　lower　the　ignition　temperature　of　CO　and　have　increased　catalytic　properties.　(C)　2008　Elsevier　B.V.　All　rights　reserved.