We used a chemical reduction method to synthesize the catalysts of cobalt (Co) and cobalt-ruthenium (Co-Ru) bifunctional supported on carbon nanotubes (CNTs) for Fischer–Tropsch synthesis (FTS) in a fixed-bed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co (0.1 to 0.4 wt%) with keeping a fixed amount of cobalt (10 wt%). Moreover, for comparison purpose, CNTs supported Co- and Co (Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy–dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), Brunauer–Emmett–Teller (BET), Hydrogen-Temperature-Programmed Reduction (H 2 -TPR), Hydrogen-Temperature-Programmed Desorption (H 2 -TPD) and O2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst pre-pared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demon-strated that the use of chemical reduction method led to decrease the average Co oxide cluster size to 8.7 nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons (C5 ), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/ γ -Al2O3 (61.20%), Co/CNTs (43.68%) and Co/ γ -Al2O3 (37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C5 selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst.