The effect of co-feeding CO2 on the catalytic properties of an Fe-Mn catalyst during Fischer-Tropsch synthesis (FTS) was investigated in a spinning basket reactor by varying added CO2 partial pressure in the feed gas. It was found that co-feeding CO2 to Syngas did not decrease the activity of the catalyst, on the contrary, a dramatic increase of the activity and an increase of methane selectivity were observed over the catalyst after removal of CO2 from the feed gas. The addition of CO2 led to an increase in olefin/paraffin ratios of low carbon hydrocarbons and a slight decrease in C-19(+) selectivity. It also slightly decreased CO2 formation rate on the catalyst by increasing the rate of reverse step of the water-gas shift (WGS) reaction and pushing the reaction towards equilibrium, and did not remarkably influence the hydrocarbon formation rate. However, the co-feeding CO2 can significantly increase the water formation rate and the overall oxygenate formation rate under these reaction conditions. (c) 2007 Elsevier B.V. All rights reserved.