The invention discloses a synthesis method of a polysubstituted benzo[c, d] indole compound. The synthesis method comprises the following steps: taking an 8-alkynyl naphthylamine compound, a catalystand alkali according to a molar ratio of 1:(0.1-0.5):(1-2), and putting into a reaction container; adding a solvent into the reaction container until the 8-alkynyl naphthylamine compound is totally dissolved; putting the reaction container in an oil bath at 0-100 DEG C, and stirring for reacting for 0-24h; cooling to room temperature; filtering with kieselguhr or silica gel powder; flushing the filter residue with dichloromethane for 2-4 times; combining the filtrates and performing reduced-pressure distillation to remove the solvent; separating with a silica gel chromatographic column, and performing reduced-pressure distillation to obtain the polysubstituted benzo[c, d] indole compound. According to the synthesis method disclosed by the invention, the polysubstituted benzo[c, d] indole compound is synthesized by a one-pot one-step process, the processes of intermediate separation and purification are reduced, and the operation method is simple; moreover, the reaction conditions are mild, the reaction selectivity is high, the yield is high, the substrate is widely applicable, the reaction raw materials are simple and easily available, and the production cost is low; the synthesismethod is suitable for small-scale preparation in a laboratory as well as industrial large-scale production.