The FTS(Fischer-Tropsch synthesis) was carried out over precipitated iron-based catalysts with or without SiO2 in a fixed-bed reactor at 250 ℃ and 1.5 MPa. The catalysts with SiO2 showed much higher catalytic activity for the FTS than those without SiO2, displaying excellent stability during 144 h of reaction. The X-ray diffraction and N2 physisorption revealed that the catalysts with SiO2 showed enhanced dispersion of Fe2O3 compared with those without SiO2. Also, the results of temperature-programmed reduction by H2 showed that the addition of SiO2 markedly promoted the reduction of Fe2O3 into Fe3O4 and FeO at low temperatures below 260 ℃. In contrast, surface basicity of the catalysts, which was analyzed by temperature-programmed desorption of CO2, decreased as a result of SiO2 addition. We attribute the high and stable performance of the catalysts with SiO2 to the improved dispersion and reducibility by the SiO2 addition.