The invention discloses a preparation method of methyl R-(+)-2-{4-[3-chloro-5-(trifluoromethyl)-2-pyridinyloxy]phenoxy}propanoate. The preparation method comprises the following sequential steps: preparing hydrogen peroxide catalyst, methyl (S)-2-chloropropionate, 2,3-dichloro-5-trifluoromethyl pyridine and 3-chloro-2-(4-hydroxy phenoxy)-5-trifluoromethyl pyridine, and finally preparing methyl R-(+)-2-{4-[3-chloro-5-(trifluoromethyl)-2-pyridinyloxy]phenoxy}propanoate. The preparation method has the advantages that: the method is simple and convenient to operate; chiral property of hydrogen peroxide is effectively utilized; and as a catalyst, hydrogen peroxide has good catalysis effect; few byproducts are produced; the yield is high and the purity is high; and the method is suitable for large-scale production.