The invention discloses(Z)-1-methyl-4-((2-selenocyanatovinyl)sulfonyl)benzene and a synthesis method thereof. The (Z)-1-methyl-4-((2-selenocyanatovinyl)sulfonyl)benzene is synthesized by performing athree-component addition reaction on ethynylaryl sulfone, potassium selenocyanate and water under the catalytic action of a biomass eutectic solvent and the action of ultrasonic waves. The (Z)-1-methyl-4-((2-selenocyanatovinyl)sulfonyl)benzene has a selenocyanate active group, and modifiable alkenyl and sulfone groups, and provides important organic intermediate for pharmaceutical synthesis. Moreover, the method has the advantages of ready availability of raw materials, simple, convenient, mild and green reaction conditions, high reaction selectivity and yield, excellent compatibility of substrate functional groups, and higher application value.