Fe-Mn-V-K catalysts for the synthesis of light olefins from CO hydrogenation were prepared by a specially controlled degradation method. The effect of the V content on the structure and the catalytic performance of the catalysts were investigated in a continuously stirred tank slurry reactor. Mo¨ssbauer spectra (MES) results show that the incorporation of V with appropriate contents can improve the dispersion of the α-Fe2O3 phase. CO hydrogenation results indicate that a small addition of V can improve the product distribution. The addition can also increase the selectivity to light olefins by inhibiting the secondary hydrogenation reaction of the initial olefin. The best catalytic performance was obtained at the Fe/Mn/V molar ratio of 3/1/0.2. The total C2-C4 content in all hydrocarbons and O/P in the C2-C4 fraction were 49.15 wt% and 3.95, respectively.