Abstract: A micro-spherical Fe-based catalyst for a slurry bed Fischer-Tropsch synthesis (FTS) comprises Fe as its active component, a transitional metal promoter M, a structure promoter S and a K promoter. The transitional metal promoter M is one or more selected from the group consisting of Mn, Cr and Zn, and the structure promoter S is SiO2 and/or Al2O3. The weight ratio of the catalyst components is Fe: transitional metal promoter: structure promoter: K=100:1-50:1-50:0.5-10. Preparation method of the catalyst comprises: adding the structure promoter S into a mixed solution of Fe/M nitrates, then co-precipitating with ammonia water to produce a slurry, filtering and washing the slurry to produce a filter cake, adding the required amount of the K promoter and water to the filter cake, pulping and spray drying, and roasting to produce the micro-spherical Fe-based catalyst for the slurry bed Fischer-Tropsch synthesis.