The effect of adding SiO2 to a precipitated iron-based Fischer-Tropsch synthesis (FTS) catalyst was investigated using N-2 physical adsorption, H-2 differential thermogravimetric analysis, temperature-programmed reduction/desorption (TPR/TPD) and Mossbauer spectroscopy. The FTS performances of the catalysts with or without SiO2 were compared in a fixed bed reactor. The characterization results indicated that SiO2 facilitates the high dispersion of Fe2O3 and significantly influences the Fe/Cu and Fe/K contacts, which play an important role in the surface basicity, reduction and carburization behaviors, as well as the FTS performances. The incorporation of SiO2 enhances the Fe/Cu contact, further enlarges the H-2 adsorption and promotes the reduction of Fe2O3 -> FeOx, while the transformation of FeOx -> Fe is suppressed probably due to the strong Fe-SiO2 interaction. SiO2 indirectly weakens the surface basicity and severely suppresses the carburization and CO adsorption of the catalyst. In the FTS reaction, it was found that SiO2 decreases the FTS initial activity but improves the catalyst stability. Due to the lower surface basicity than the catalyst without SiO2, the catalyst incorporated with SiO2 has higher selectivity to light hydrocarbons and methane and decreased selectivity to the olefins and heavy hydrocarbons. (c) 2006 Elsevier B.V. All rights reserved.