Abstract: Silylated SiO₂ with different hydrophobicities was prepared before the impregnation of cobalt precursor to obtain Co-based catalysts in Fischer-Tropsch synthesis. The effect of silylation on the crystallite structure and reduction behaviors of the resultant cobalt catalysts was investigated by FT-IR, ²⁹Si CP MAS NMR, N₂ sorption, XRD, Raman, XPS, and H₂-TPR; their catalytic performance in Fischer-Tropsch synthesis was evaluated in a fixed-bed reactor under 2.0 MPa, 240 ℃, n(H₂)/n(CO) ratio of 2, and space velocity (GHSV) of 1 000 h^-1. The results indicated that compared with unsilylated SiO₂, silylated SiO₂ leads to larger and more perfect Co₃O₄ crystallite, weaker interaction between cobalt and silica, and higher reducibility; As a result, the activity of cobalt catalysts is enhanced and higher CO conversion is achieved for Fischer-Tropsch synthesis.