Abstract: A series of cobalt-based catalysts were prepared by incipient wetness impregnation, using Degussa A300 and R106 as supports. The physico-chemical properties of samples were characterized by XRD, BET, TPR, TPO and FT-IR. Fischer-Tropsch (F-T) reaction was carried out in a fixed-bed reactor under the conditions of n(H2)/n(CO) = 2.0, GHSV = 1500h－1, p= 2.0MPa and t=210℃～ 260℃. The investigation showed that there was some relation between the Co3O4 size and the coverage of hydroxyl on the surface of supports. Organic groups covering hydroxyl on surface of support weakened the interaction strength of support-precursor combinations, and that favored the formation of Co3O4 with bigger crystallite size. The sintering of organic groups made the reaction activity and the selectivity for heavy hydrocarbons decrease.