Abstract: Despite that iron-based catalysts are preferred for the high selectivity to value-added α-olefins via Fischer-Tropsch synthesis (FTS) reaction, the carbon deposition leads to deactivate catalyst more readily and CO₂ selectivity as high as ~50% leads to low carbon efficiency. Herein, we developed an innovative approach to fabricate iron-based catalysts to deal with this issue. In detail, Fe₃O₄ microspheres with an average particle size of ~580 nm were prepared via hydrothermal method and mixed with GO. The GO modification can effectively inhibit the sintering and coking of the large Fe₃O₄ microspheres (580 nm) by assisting its evolution into much smaller iron carbide nanocapsules (~9.1 nm). The obtained catalyst exhibits excellent reaction activity, stability and high α-olefin selectivity. The addition of K into Fe₃O₄ microsphere produces major ε′-Fe_2.2C about 58.9% in the evolution process and facilitates lower CO₂ emission obviously.