The invention relates to a synthesis method of N alpha-t-butyloxycarboryl-DL-m-hydroxy tyrosine, which mainly solves the technical problems that the existing synthesis method is higher in cost and high in pollution, generates many byproducts and is adverse to mass production. The synthesis method comprises the following steps: dissolving DL-m-hydroxy tyrosine in a buffer solution prepared by anhydrous sodium carbonate an anhydrous sodium bicarbonate, performing stirring for intensive dissolution, slowly dropwise adding di-tert butyl dicarbonate mixed solution where acetone is dissolved at 0 DEG C, keeping a pH (pondus hydrogenii) value of a reaction solution to be 8-9 with a sodium carbonate aqueous solution, tracking a reaction endpoint through TLC (thin-Layer chromatography), after a reaction is finished, performing filtration, washing unreacted di-tert butyl dicarbonate in filtrate using an ethyl acetate and petroleum ether mixed solution, adding an extraction agent, ethyl acetate,into a water phase, performing acidification using solid citric acid, controlling the pH value to be 3-5, permitting standing and layering, tracking a byproduct through the TLC, washing an oil phase,performing drying and reduced pressure distillation, and adding petroleum ether for crystallization to form N alpha-t-butyloxycarboryl-DL-m-hydroxy tyrosine. N alpha-t-butyloxycarboryl-DL-m-hydroxy tyrosine is a raw material for synthesizing a polypeptide drug.