New synthetic method for methyl-7-iodoheptanoate was studied. Methyl-7-iodoheptanoate is important compound in the synthesis codlemone, the sex pheromone of codling moth which doing harm to apple tree significantly, and this compound also be used essentially in the synthesis of prostaglandin derivatives. In previous the methyl-7-iodoheptanoate has been prepared from-7-chloroheptanoic acid as a starting material with disadvantage, since the 7-chloroheptanoic acid is expensive and the process is much complicate. In this paper the method to preparing methyl-7-iodoheptanoate was developed economically by using dihydropyran as a starting material in the course of 5 steps. Hence, methyl-7-iodoheptanoate which can be synthesized by new method studied onthis paper should be very useful compound for preparing codlemone or its acetate which will be used to developing pollution-free insecticides, and for preparing prostaglandin derivatives with advantage.