The invention discloses a preparation method of methoxyfenozide and relates to the field of insecticide, and particularly relates to the preparation method of methoxyfenozide. The preparation method includes steps of preparation of 3, 5-dimethylbenzoyl
chloride: adding 3, 5-mesitylenic acid and methylbenzene in a reaction
bottle; raising temperature to 60 DEG C, and dropwise adding
thionyl chloride within 2 hours; preserving temperature for 3 hours, depressurizing and removing
solvent to obtain 3, 5-dimethylbenzoyl
chloride; synthesis of midbody: adding tert-butylhydrazine,
sodium hydroxide and methylbenzene in the reaction
bottle, and cooling to 0 DEG C; adding di-tert-butyl
dicarbonate ester and reacting for 10 hours at 0-5 DEG C; removing a
water layer, adding 3, 5-dimethylbenzoyl chloride and
sodium hydroxide solution in an
organic layer; reacting for 4 hours at 0-5 DEG C, filtering a product and adding the
filter cake in
methanol; adding
hydrochloric acid in the reaction mixture;reacting for 20 hours at 35 DEG C; filtering the product, washing and
drying to obtain the midbody. The preparation method is simple in operation, safe and reliable in reaction; the production efficiency is greatly improved, and the production cost is reduced; moreover, the product is high-efficient, low-toxic and environment-friendly.