An organic base modified composite catalyst for producing ethylene by hydrogenation of carbon monoxide is a composite catalyst and formed by compounding component I and component II in a mechanical mixing mode. The active ingredient of the component I is a metal oxide; the component II is an organic base modified zeolite of MOR topology; and a weight ratio of the active ingredients in the component I to the component II is 0.1-20, and preferably 0.3-8. The reaction process has an extremely high product yield and selectivity. The selectivity of C2-C3 olefins is as high as 78-87%; the selectivity of hydrocarbon products with more than 4 C atoms is less than 10%; the selectivity of a methane side product is extremely low (