The TPSR technique was used to investigate the effect of the support on the secondary reactions of ethylene formed during CO hydrogenation. Based on the results of CO hydrogenation and CO/H-2-TPSR characterization, it was found that different supports induced different secondary reactions, and thus affected the selectivity to light olefins directly. The Fe-MnO/MgO catalyst (basad on basic support) causes disproportionation Of C2H4, and thus, leads to the formation Of C3H6. The Fe-MnO/Al2O catalyst (based on acidic support) showed obvious hydrogenation Of C3H6. The disproportionation Of C2H4 was also promoted by the Fe-MnO/Al2O3 catalyst, but because of its activity for C3H6 hydrogenation, a large amount of C3H8 was produced. The different C2H4 secondary reactions arc relevant to different CO/H-2 reaction pathways over the catalyst surface, so the Fe-MnO/MgO catalyst is a desirable catalyst for the production of light olefins from CO/H2 while the Fe-MnO/Al2O3 catalyst was not so.