NOVELTY - Purifying 2-(4-methyl phenyl) propionic acid involves using 2-(4-methyl phenyl) propionic acid as initial raw material, simple substance bromine for bromination reaction to replace other single organic solvent with aqueous and organic solvent two-phase system of a reaction system, free radical initiation in a two-phase system, or light to initiate reaction, or free radical initiator to initiate reaction, then cleaning by hydrogen peroxide, oxidation hydrobromic acid oxidation recycling.    USE - For purifying 2-(4-methyl phenyl) propionic acid (claimed).    ADVANTAGE - The purification method overcomes many disadvantages of present method of bromide, is of low cost, environment-friendly, realizes zero pollution process of the production process; improves synthesis process. The method yield 2-(4-methyl phenyl)propionic acid, for large scale industrial green production.    DETAILED DESCRIPTION - Purification of 2-(4-methyl phenyl) propionic acid involves: in reaction container, adding 2-(4-methyl phenyl) propionic acid and dissolving it in organic solvent, water and fully stirring and reducing temperature to 10-20 degrees C, then under the illumination condition under condition of stirring, dropping bromine reaction solution, or heating to reflux, while stirring, the reaction liquid bromine, where the bromine reaction liquid comprises free radical initiator, organic solvent, and bromine solution; adding the reaction solution of bromine semi-after adding hydrogen peroxide solution into the reaction solution, adjusting adding speed of the two, where the two are close to at the same time are added, and then continuing to react the original light or heating under the condition of without changing the sampling monitor, to complete the 2-(4-methyl phenyl) propionic acid reaction, stopping stirring, separating and removing aqueous phase layer; collecting and combining all the organic phase layer, separating and purifying to obtain 2-(4-methyl phenyl) propionic acid. The 2-(4-methyl phenyl) propionic acid and bromine is present in a molar ratio of 1.0:0.56-0.62. The 2-(4-methyl phenyl) propionic acid and free radical initiator is present in a molar ratio of 1:0.32-0.36. The 2-(4-methyl phenyl) propionic acid with hydrogen peroxide is present in a molar ratio of 1:1.1-1.2. The 2-(4-methyl phenyl) propionic acid and water is present in a molar ratio of 1:1.6-2. The 2-(4-methylphenyl) propionic acid and organic solvent mass-to-volume ratio (g/ml) is 1:7.9-8.3.