NOVELTY - Synthesis of 4-amino-phenylbutyric acid hydrochloride involves adding benzaldehyde and ethyl acetoacetate to ethanol, reacting while stirring at room temperature for 46-50 hours, filtering, catalyzing filter cake with organic alkali, washing filter cake with ethanol, drying filter cake to obtain first solid, concentrating filtrate, cold separating, alcohol washing, filtering to obtain second solid, combining solids to obtain first intermediate, adding 20 wt.% sodium hydroxide solution to first intermediate, reacting while stirring at 85-90 degrees C for 2-2.5 hours, filtering and water washing.    USE - Method for synthesizing 4-amino-phenylbutyric acid hydrochloride (claimed).    ADVANTAGE - The method has simple process, high yield, low cost and no pollution.    DETAILED DESCRIPTION - Synthesis of 4-amino-phenylbutyric acid hydrochloride comprises:    (A) adding benzaldehyde and ethyl acetoacetate to ethanol, reacting while stirring at room temperature for 46-50 hours, filtering, catalyzing filter cake with organic alkali, washing filter cake with ethanol, drying filter cake to obtain first solid, concentrating filtrate, cold separating, alcohol washing, filtering to obtain second solid and combining solids to obtain first intermediate;    (B) adding 20 wt.% sodium hydroxide solution to first intermediate, reacting while stirring at 85-90 degrees C for 2-2.5 hours, filtering, water washing filter cake, combining filtrates, cooling while stirring for 3 hours, adding dropwise hydrochloric acid solution, regulating pH to 1-2, filtering, water washing and drying to obtain solid second intermediate;    (C) dissolving second intermediate in pure acetic acid anhydride solution and toluene, refluxing for 3-5 hours, concentrating to remove acetic acid anhydride, dissolving in methylbenzene, adding ammonia water, reacting at 60-65 degrees C for 1-1.5 hours, adding dropwise sulfuric acid, regulating pH to 1-2, separating solid, filtering, water washing and drying to obtain solid third intermediate;    (D) dissolving third intermediate in 25 wt.% sodium hydroxide solution, cooling to - 5 to 10 degrees C for 15-20 minutes, slowly adding sodium hypochlorite, reacting under ice bath for 0.5-1.5 hours, heating at 60-80 degrees C for 1-1.5 hours, re-cooling for 5 hours, adding dropwise hydrochloric acid, regulating pH to 2, stirring at room temperature, decoloring, filtering, adding sodium hydroxide, regulating pH to 6-7, cooling, stirring for 2 hours and filtering to obtain 4-amino-3-phenylbutyric acid; and    (E) dissolving 4-amino-3-phenylbutyric acid in 18 wt.% diluted hydrochloric acid, concentrating to dryness, adding 95% ethanol, heating to dissolve and recrystallizing.