Barium modified Co/Al2O3 catalysts were prepared by incipient wetness impregnation.The catalysts were characterized by XRD,TPD and DRIFTS.The catalytic activity for Fischer-Tropsch synthesis was measured in a continuously stirred tank reactor.It was found that small amounts of BaO(≤2 wt%) improved the cobalt reducibility,which led to more cobalt active sites on the catalyst surface,and then resulted in higher CO conversion and C5+ selectivity.However,for the catalysts with high BaO loadings negative effects on the catalytic activity and selectivity for high hydrocarbons were observed because of low cobalt reducibility.