The catalyst Co-Ph3PO/PDMS/SiO2, Co-Ph3PO complex immobilized on polydimethylsiloxane (PDMS) functionalized SiO2, was prepared by sol-gel method. The characterizations of the catalysts were made by FT-IR, ICP-AES and N-2 adsorption/desorption. The BET surface area, pore diameter and pore volume of the catalyst Co-Ph3PO/PDMS/SiO2 were smaller than that of pure SiO2 center dot ICP-AES showed that the content of cobalt of Co-Ph3PO/SiO2 was almost the same as that of Co-Ph3PO/PDMS/SiO2. The conversion of mixed octenes catalyzed by Co-Ph3PO/PDMS/SiO2 was 24.6 % (cobalt leaching was only 0.014% after the first run), which was two times about that of Co-Ph3PO/SiO2 (the conversion was only 11.6 , 25% cobalt leaching was observed after the first run). The immobilized catalyst Co-Ph3PO/PDMS/SiO2 could be reused six times without reducing the activity and selectivity.