The invention relates to a method for preparing 2-(4-methoxy phenoxy) propionic acids. The method includes adding, by weight, 183 parts of
hydroquinone and 202.5 parts of S-methyl 2-chloropropionate into a reaction kettle, adding, by weight, 100 parts of
sodium hydroxide for a first batch, raising the temperature of the reaction kettle to 70 DEG C to 80 DEG C, reserving the temperature for 8 hours, and reducing the temperature of the reaction kettle to the
room temperature after reaction; adding, by weight 128 parts of
hydrochloric acid into the reaction kettle, keeping the pH to be about 5 to 6, and reacting the
hydroquinone with the
hydrochloric acid in a weak acidic environment to produce
hydroquinone; adding an extracting agent 4-methyl-2-
pentanone into the reaction kettle, layering the solution, wherein an
organic layer is the hydroquinone and the extracting agent, and a
water layer is an intermediate A / B,
methanol and a
salt solution; separating an organic phase mixture, reducing the pressure to distill the 4-methyl-2-
pentanone, and subjecting hydroquinone crystals to
centrifugal separation; and adding, by weight, 128 parts of hydrochloric acids into a dealcoholized aqueous phase, regulating the pH to be 1 to 2, reacting the intermediate under an acid
precipitation condition, and precipitating the 2-(4-methoxy phenoxy) propionic acids after adding acids. The method for preparing 2-(4-methoxy phenoxy) propionic acids has the advantages of being simple to operate, low in cost, small in
pollution, and suitable for industrial large scale application.