The present invention provides an iron-based catalyst for low-carbon olefin production through CO2 hydrogenation, wherein the main active component of the catalyst is Fe3O4, the auxiliary agent is added or is not added, and is an oxide, the content of the auxiliary agent accounts for 0-30% of the total mass of the catalyst, and the auxiliary agent is one or more than two selected from the oxide of Si, Al, Mn, K, Cu, Na, Zr, V, Zn and Ce. The present invention further provides a preparation method and applications of the catalyst. According to the present invention, the catalyst has the following beneficial effects that 1) the particles have characteristics of regular spherical shape, uniform spatial distribution, and narrow size distribution; 2) the raw materials are inexpensive and easy to obtain, and the preparation method has characteristics of simpleness and low cost, and is suitable for industrial production; 3) the catalyst has characteristics of high mechanical strength, good wear resistance and compression resistance, and is suitable for the fixed bed, the fluidized bed and the slurry bed; 4) the CO2 hydrogenation activity and the low-carbon olefin selectivity are high, the single-pass conversion rate can achieve more than 40%, the methane selectivity in the hydrocarbon product is lower than 15%, the low-carbon olefin selectivity is higher than 40%, the alkene/alkane ratio (O/P) is 2-12, and the yield of the low-carbon olefin can achieve 10-60 g/m<3> (CO2+H2).