The fluctuation of crude oil prices is presently reach ing a crisis. The root of this problem has emerged from the fact that a petroleum resource has been continuously depleted and couldn’t meet the demand. A renewable energy derived from biomass has become one of the very promising resources in Thailand. Biomass alteration through gasification has gained more attentions recently. The biomass derived syngas mainly comprises CO (g) and H2 (g), which is suitable for being the feed reactant for the Fischer-Tropsch (FT) process to produce liquid fuel. The present research aims to investigate a continuous FT fixed-bed reactor, which is an essential component of a liquid-fuel production process from biomass. The pilot scale fixed bed reactor (diameter of 10 cm, height 90 cm) was adopted in this study. Three steady-state experiments were performed for finding optimum operating conditions. Continuous feeds of modeled syngas of 6, 18, and 29 slpm (H 2 /CO molar ratio 2/1) were passed onto a fixed Ru supported alumina catalyst bed. The reactions were carried out at 180-220˚C and 1-3 bars. The experimental results revealed that the CO conversion for the case using the syngas of 6 slpm gave the highest conversion of 66.7% and the highest overall selectivity of 67.29% (C5+)