The invention belongs to the field of organic synthesis, and discloses a synthesis method of an iodine-catalyzed 3-arylthio imidazo [1,5-a] N-heterocyclic compound. The synthesis method comprises the following steps of sequentially adding an imidazo [1,5-a] N-heterocyclic compound, a diaryl disulfide compound and a catalyst into a reaction tube, performing dissolution with 1-2ml of dimethyl sulfoxide (DMSO), performing heating to 100-120 DEG C, and performing a reaction for 6-10h; and after the reaction is completed, cooling reaction liquid to room temperature, and performing post-treatment so as to obtain a 3-position sulfenylation imidazo [1,5-a] N-heterocyclic compound. The invention firstly provides the synthesis method of the sulfenylation imidazo [1,5-a] N-heterocyclic compound; the synthesis method has the characteristics that the participation of transition metal is not needed, reaction conditions are mild, the range of a substrate is wide, and the yield is high; and the synthesis method has wide application prospects in the fields of pharmacy and fluorescent materials.