Co/SiO2 catalysts were prepared by sol-gel method with varied en (ethylenediamine)/Co molar ratios under the same pH. Their physical-chemical properties were compared with those prepared with similar en/Co molar ratios at natural pH or without adding ethylenediamine. Regardless of pH, the catalysts prepared using ethylenediamine possessed high microporosity, which led to a better selectivity to C5-18 hydrocarbons, versus the catalyst possessing higher mesoporosity which showed slightly higher C18+ selectivity. As enough positions in the coordination sphere were blocked by ethanediamine ligands, the formation of cobalt silicate disfavored for (en/Co=2) catalysts, which resulted in the higher activity in FT reaction. Whereas the catalysts prepared with lower or higher en/Co molar ratio both showed lower activity due to the formation of [(SiO)Co(en)(EtOH)3] species or the electronic adsorption of cobalt complexes in the negatively charged silica surface, respectively. However, for the catalyst without using ethylenediamine, the lowest activity and the highest CH4 selectivity obtained due to its much lower reducibility.