This work deals with the improvement of diesel (C-10-C-20) production of Fischer-Tropsch (FT) synthesis at low pressure over Co-Re/Al2O3 since high catalytic activity and great potential in producing C-10-C-20 hydrocarbons were observed under conventional conditions. To improve the catalytic performance, CO conversion and hydrocarbon selectivity were investigated against pressure, syngas H-2/CO ratio, gas flow rate, and temperature. 93.7% of CO conversion was achieved as well as 62.3% diesel selectivity over Co-Re/Al2O3 catalyst even after working for 15 days, which was far higher than the maximum value of the Anderson-Schulz-Flory (ASF) distribution and the results in literature reports. It is suggested that Re plays an important role in enhancing dissociation of hydrogen as well as the formation of CH, CH2, and CH3 species to convert CO.