The invention relates to a synthetic method of 5-vinyl-2-norbornene.The synthetic method is characterized by including adding 1,3-butadiene and cyclopentadiene serving as substrates and supercritical carbon dioxide serving as a solvent into a reaction kettle, reacting at 150-215 DEG C for 15-300 minutes, and subjecting a product to quick cooling and quenching reaction after the reaction is terminated, wherein a molar ratio of 1,3-butadiene to cyclopentadiene is 0.8-2.0:1, and density of the carbon dioxide is 0.2-0.8 g/cm<3>; emitting the carbon dioxide in the reaction kettle, taking out a reaction solution and separating so as to obtain the 5-vinyl-2-norbornene.The synthetic method of the 5-vinyl-2-norbornene has the remarkable advantages that green technologies are achieved, actual conversion rate of the cyclopentadiene is above 30%, and polymer generation is inhibited greatly without use of a polymerization inhibitor.