Abstract: Selective synthesis of jet fuel-range hydrocarbons (C_8~18) was investigated in a fixed-bed reactor over Ru modified cobalt-based catalysts, supported on mesoporous SiO₂ and microporous HZSM-5. The effect of Ru adding amount (1%~4%) and the textual and structural properties of the catalysts on Fischer-Tropsch synthesis(FTS) performance were studied. The results showed that the tailor-made Ru-Co/SiO₂/HZSM-5 catalysts maintained both meso-and micro-pores. Co dispersion and reducibility at 150~750 ℃ were enhanced with the increase of Ru amount, which resulted in the increase of CO conversion. In the same time, the yield of iso-paraffins was enhanced due to the existence of microporous structure of HZSM-5. Thus CO conversion of 62.8% and yield of jet fuel-range hydrocarbons (C_8~18) of 37.7%, including 10.9% of iso-paraffins, were achieved over 1% Ru modified Co/SiO₂/HZSM-5. The FTS product distribution shifted to low-carbon hydrocarbons when Ru amount was higher than 2% due to the increased CO hydrogenation rate and CH₄ selectivity.