The traditional Fischer-Tropsch synthesis focuses on the production of long chain saturated hydrocarbons such as wax/oil, of which the “metal/acidic oxide” interface of the catalysts can polarize and stabilize the reaction intermediates, thus promoting hydrogenation and C—C coupling, and contributing to the formation of longer chain alkanes. However, lower olefins are unsaturated short-chain hydrocarbons. In order to obtain high value-added lower olefins directly from syngas, the design concept should be the opposite of the traditional Fischer-Tropsch method for the purpose of producing long-chain alkanes. Therefore, we focus on the fundamental research of the "weak hydrogenation metal/solid base support" Fischer-Tropsch to olefins catalysts, use the surface basic support and basic potassium promoter to reverse the status of above-mentioned interface between "metal/acid oxide" in the traditional catalysts, weaken the promotion of hydrogenation and C—C coupling, and achieve the purpose of inhibiting hydrogenation and C—C coupling. The ratio of olefin to paraffin (O/P) of a Fe/K/Mg—O—Al series catalyst depends on its integral area of the high temperature peak in CO2-TPD profile. Under the same passivation treatment at 1200℃, compared with the weak base catalyst supported by simple oxide MgO, the strong base catalyst supported by composite oxide MgAl2O4 significantly increased the hydrocarbon product distribution value of C2=-C4= hydrocarbon by 84%, and the C2-C4 olefin/paraffin ratio by 266%.