The invention belongs to the technical field of drug synthesis and particularly relates to a preparation method of a hinokitiol intermediate 7,7-dichloro-3-isopropyl bicyclo[3.2.0] heptyl-2-alkenyl-6-ketone. The method comprises the steps that dichloracetyl chloride and tripropylamine form dichloroethylene, then the dichloroethylene is added with 1-isopropyl cyclopentadiene to prepare a ketene addition product, the tripropylamine is used as organic base in 2+2 addition, and the tripropylamine adopts base added layering in a water phase for recovery and reuse after reaction is complete. By adopting the method, it can be ensured that the reaction reagent with low water content is easy to recover while the reaction is smoothly performed.