Co/SiO2 catalysts with 0.4-7.0 wt.% of Mn addition were prepared and evaluated for Fischer-Tropsch synthesis (FTS), using H-2-deficient biosyngas (H-2/CO/CO2/N-2 = 45/45/7/3, vol%) as feed gas. 0.8 wt.% of Mn addition to Co/SiO2 increased Co dispersion and weakened Co-Si interaction on Co-(0.8%) Mn/SiO2 catalyst. Co reducibility was improved to 32.1% and 79.3% at 150-400 degrees C and 150-750 degrees C respectively by H-2-temperature programmed reduction (TPR), which resulted in CO conversion of 52.6% and C5+ yield of 43.6% at 24 h time on stream when H-2-deficient biosyngas was used as feed gas for FTS. Co was further dispersed with low reducibility at higher Mn addition amount, which decreased CO conversion and favored gaseous hydrocarbon synthesis over Co-(2.0%) Mn/SiO2 and Co-(7.0%) Mn/SiO2. The higher H-2/CO usage ratio was obtained over Co/SiO2 using H-2-deficient biosyngas, compared with that using feed gas with H-2/CO ratio of 2.0 over the same catalyst. The existence of small amount of CO2 (like 7.0 vol%) in biosyngas might be the main reason to inhibit water gas shift reaction and impel CO2 conversion. (C) 2014 Elsevier Ltd. All rights reserved.