The invention discloses a preparation method of 4-amino-7-iodo pyrrolo [2, 1-f] [1, 2, 4] triazine, which comprises the following steps: reacting 4-amino pyrrolo [2, 1-f] [1, 2, 4] triazine with an iodine-containing substance and an oxidant to obtain 4-amino-7-iodo pyrrolo [2, 1-f] [1, 2, 4] triazine; wherein the iodine-containing substance is iodine or a hydroiodate; the oxidantis at least one ofpotassium hydrogen persulfate composite salt, hydrogen peroxide, m-chloroperoxybenzoic acid, tert-butyl hydroperoxide, sodium hypochlorite, ammonium persulfate and sodium persulfate. According to thepreparation method disclosed by the invention, the preparation is simpler, and the 4-amino-7-iodo pyrrolo [2, 1-f] [1, 2, 4] triazine can be obtained in one step; the preparation method has the characteristics of readily available and cheap raw materials, simple process, mild reaction conditions, high product yield, high iodine atom utilization rate and the like.