The present invention discloses catalyst and method for producing light olefins directly from synthesis gas by a one-step process, and particularly relates to method and catalyst for directly converting synthesis gas into light olefins by a one-step process. The provided catalysts are composite materials formed of multicomponent metal oxide composites and inorganic solid acids with hierarchical pore structures. The inorganic solid acids have a hierarchical pore structure having micropores, mesopores and macropores. The metal composites can be mixed with or dispersed on surfaces or in pore channels of the inorganic solid acid and can catalyze the synthesis gas conversion to a C2-C4 light hydrocarbon product containing two to four carbon atoms. The single pass conversion of CO is 10%-60%. The selectivity of light hydrocarbon in all hydrocarbon products can be up to 60%-95%, wherein the selectivity of light olefins (C2═—C4═) is 50%-85%.