Abstract: A preparation process of 5-ethylidene-2-norbornene, including: introducing dicyclopentadiene into a dicyclopentadiene decomposition reactor to thermally decompose the dicyclopentadiene; introducing a product of the above step into a cyclopentadiene purification tower; introducing 1,3-butadiene, a solvent, and cyclopentadiene separated from the top of the cyclopentadiene purification tower into a Diels-Alder reactor to react the same; introducing a product of the immediate above step into a 1,3-butadiene removal tower to recover 1,3-butadiene from the top; introducing a mixture at the bottom of the 1,3-butadiene removal tower into a desolvation tower, and recycling a solvent and unreacted raw materials recovered from the top of the desolvation tower to the dicyclopentadiene decomposition reactor; introducing a mixture at the bottom of the desolvation tower into a 5-vinyl-2-norbornene separation tower to separate 5-vinyl-2-norbornene; and introducing the 5-vinyl-2-norbornene into an isomerization reactor to rea