An amorphous Co-B catalyst was prepared by chemical reduction method and characterized by isothermal N-2 adsorption/desorption, XRD, ICP-AES and HR-TEM. The catalytic activity of the Co-B catalyst in the hydroformylation of 1-octene was evaluated in a 100 mL stainless autoclave. Fresh amorphous Co-B catalyst showed a relatively high activity in the hydroformylation of 1-octene. The thermal stability of fresh Co-B catalyst was also examined. When fresh Co-B catalyst was thermally treated in N-2 or H-2 atmosphere at 200-500 A degrees C for 2 h, the specific surface area and the catalytic activity of the Co-B catalyst decreased. When Co-B was supported on SiO2, the activity of the catalyst increased obviously. Compared with conventional supported Co/SiO2 catalyst, Co-B/SiO2 showed much higher activity than Co/SiO2. The influences of solvents and reaction conditions on the catalytic activity of the amorphous Co-B catalyst were also studied. The recycle test of the amorphous Co-B catalyst was done.