The invention discloses a catalyst for directly preparing high-carbon olefin from methane through microwave assistance and a catalysis technology. The catalysis technology is characterized by firstlycarrying out catalytic dehydrogenation coupling on the methane through nickel powder under the conditions of microwave-assisted heating and induction and excessive hydrogen, then carrying out catalytic oligomerization under the action of a nickel-molybdenum composite catalyst, carrying out purification by rectification on an oligomerization product, carrying out condensation polymerization under the action of external heating and the nickel-molybdenum composite catalyst, and highly selectively synthesizing high-carbon olefin liquid fuel. According to a method disclosed by the invention, the conversion rate of the methane is 70 to 75 percent, the selectivity on an intermediate-butylene is 99 percent, the conversion rate of butylenes condensation polymerization reaction is 91.1 percent, thecontent of a dimer-C8 olefin in a product is 89.2 percent (by weight), and the content of a trimer C12 olefin in the product is 10.8 percent (by weight); the method takes natural gas or biomethane asan original raw material, and has the characteristics of high selectivity of high-carbon olefin, environmental friendliness, energy saving, low cost, no toxicity of the catalyst and no pollution.