The invention discloses a method for synthesizing 2,6-dimethyl phenoxyacetic acid, comprising the following steps of: (1) adding 2,6-dimethyl phenol to an alkali aqueous solution, wherein the 2,6-dimethyl phenol and alkali are added in the mole ratio of 0.5-1.0:1.0; (2) stirring to dissolve the mixture, then filtering after sufficient reaction, increasing the temperature of a filtering material and dewatering to obtain 2,6-dimethyl phenolate; (3) mixing the 2,6-dimethyl phenolate and chloroacetic acid in the mole ratio of 0.5-1.0:1.0, heating till the 2,6-dimethyl phenolate and the chloroacetic acid are completely melted, and reacting in an inert gas atmosphere; (4) after the reaction is finished, cooling to room temperature, adding water or alkali liquor for washing, and filtering to obtain a crude product; and (5) recrystallizing the crude product to obtain a 2,6-dimethyl phenoxyacetic acid pure product. The synthesizing method has the advantages of simple and convenient operation, short reaction time, easy postprocessing, few side product, high productivity, and the like.