Abstract: The effect of space velocity on FT reaction has been evaluated over a 10%Co/TiO2 catalyst prepared by incipient wetness impregnation method. The catalyst was tested in a fixed-bed reactor at 220oC, 20 bar and various feed gas space velocities (20, 40 and 60 Nml/gCat/min). The CO consumption rate, olefin to paraffin ratio, C5+ selectivity and the chain growth probability (alpha) were found to increase with an increase in feed gas flow rate. The results were explained in terms of reactants partial pressures and mass transfer in the reactor as function of CO conversion levels