The invention discloses a preparation method of a p-aminophenylacetic acid, which comprises the following steps of: adding p-nitrophenylacetic acid,
ethanol and a catalyst into a pressure reaction kettle in a certain proportion, replacing air in the reaction kettle with
nitrogen, feeding
hydrogen into the reaction kettle, and controlling a certain pressure and temperature; after the reaction is performed for a period of time, standing the reaction kettle, cooling the obtained product to
room temperature, opening the pressure reaction kettle, and extracting 60-80%
solvent ethanol through evaporating; carrying out cooling
crystallization,
filtration and
drying on the
solvent ethanol so as to obtain a coarse product, and carrying out recrystallization on the coarse product by using ethanol, and carrying out
active carbon decoloration on the obtained product so as to obtain white crystalline p-aminophenylacetic acid, wherein the
mass ratio of the p-nitrophenylacetic acid, the ethanol to the catalyst is 1:10: (0.02-0.05), the
mass concentration of the ethanol is 95%, the
mass concentration of the catalyst is 3-8% Pd / attapulgite clay, the reaction pressure is 0.4-0.6 MP, the reaction time is 3-5 hours, and the
reaction temperature is 30-60 DEG C. According to the invention, the catalyst is low in cost, less in application amount and convenient for recycling; the method is mild in
reaction conditions, energy-saving and environment-friendly; the method is good in reaction selectivity, less in side effects, easy to realize purification, and high in yield; and through taking
hydrogen as a
raw material, the method is less in
pollution, simple in post-
processing, and low in production cost.