The invention provides an iron-based catalyst for preparation of low carbon olefin from synthetic gas. The catalyst contains Fe3O4 as a main
active component, and also contains one or two or above assistant M for modification, and M is selected from Si, Al, Mn, K, Cu, Na, Zr, V and Zn. The content of
oxide of the assistant in the catalyst is 0-30wt%. The catalyst has the following advantages: 1, particles of the catalyst have regular
spherical morphology, uniform space distribution, narrow dimension distribution, and average particle size of 30nm; 2, the catalyst has the characteristics of cheap and easily available raw materials, simple preparation method, low cost, and suitableness for industrial production; 3, the catalyst has good
mechanical strength,
wear resistance and compression resistance, and is suitable for being applied in fixed beds, fluidized beds and
slurry beds; and 4, the catalyst has high Fischer-Tropsch synthesis activity and high low-carbon olefin selectivity, the single-pass conversion rate can reach above 95%, the
methane selectivity is lower than 15%, the olefin / paraffin ratio (O / P) is 2-6, and the low-carbon olefin yield can reach 40-100g / m<3>(CO+H2).