In this paper, a method is adopted to combine a single-factor experiment with orthogonal experiment, and conducts a systeriaatic study on the synthesis reaction process of naphthylacetic acid. The process was served with ferric chloride as major catalyst and potassium as assistant catalyst. Our results showed that when the reaction temperature reaches about 200%, the reaction time lasts 15 hours, the molar ratio of naphthalene and chloroacetic acid is 2.5, the mass ratio of reactant and catalyst is 32.5, and the molar ratio of major catalyst and assistant catalyst is 1 to 5, the rate of production could reach 53.9%. This improved method requires less time for reaction, and increases reactive productivity than traditional method for synthesis of naphthylacetic acid.