Abstract: Hyphantria cunea is a worldwide quarantine pest that has currently inflicted substantial losses on forestry and landscape greening in China. The trapping of this pest using its sex pheromone features high selectivity, low dosage, and environmental friendliness. (3Z,6Z,9S,10R)-9,10-epoxy-3,6-heneicosadiene is one of the key components of the H. cunea sex pheromone, and the design and development of its synthetic process route are of great significance for the popularization and application of the H. cunea sex pheromone. This research designs a synthetic process route taking 2- (2-propynyloxy)tetrahydropyran as the starting material, the target molecule was synthesized with cis-selectivity of double bonds in an overall yield of 12.6% via 12 reaction steps, including nucleophilic substitution of haloalkanes, nickel acetate/sodium borohydride catalyzed hydrogenation, Appel reaction, copper-catalyzed coupling, epoxidation with m-chloroperoxybenzoic acid (m-CPBA), and ceric ammonium nitrate (CAN)-catalyzed oxidation. The main advantages of this route lie in the stable properties and easy separation and purification of the intermediates, providing a feasible technical path for the industrial preparation of this sex pheromone.