Abstract: The synthesis performance of a spray-dried spherical iron-based F-T catalyst SFT418 reduced with difference H2/CO molar ratio syngases was investigated in a continuous stirred slurry tank reactor under reaction conditions of 250℃, 2.3 MPa, H2/CO = 1.5 and 3000 ml/(g.cat?h) and the bulk composition of the catalyst after reaction was characterized by M?ssbauer (MES). The results indicate that the BET surface area and the pore volume of the reduced catalyst decrease, while the average pore size is the opposite after reduction. The catalyst is easier to reduce with low H2/CO ratio syngas and has more FexC phase and higher conversion at the start-of-run but faster deactivation rate. Higher ratios of H2/CO ratio syngas give the reversive results. It is proven that the most appropriate H2/CO molar ratio of reduction syngas is 20:1.