Synthesis of C-2-C-6 lower olefins from synthesis gas was investigated through Fischer-Tropsch synthesis (FTS) reaction over active carbon-supported iron catalyst with a small amount of Cu (Fe-Cu/AC) catalysts using a fixed bed reactor at 300 degrees C at 2.1 MPa. Mn promoted catalyst (Fe-Cu-Mn/AC) gave high yield and selectivity to the lower olefins. Added Mn species seemed likely to locate uniformly on the AC surface to form complex oxide with iron oxide. A high yield of ca. 40% is obtainable at high H-2/CO ratio of 4. The catalyst showed stable activity and selectivity for 100 h. CO2 addition in the feed gas enhances the yield further by suppressing the water gas shift reaction.