The invention relates to an industrial plant for lowering operating cost of an aromatic extraction system and an application method thereof. An anion exchange resin tower purification unit (A) is added between a lean solvent/rich solvent heat exchanger (3) and an extraction tower (1); 0-6% of sulfolane in the extraction system is introduced into the purification unit (A); the sulfolane passes through an anion exchange resin tower (15) in the purification unit (A) at the temperature of 40-60 DEG C at the volumetric space velocity of 1.5-9.0 h<-1>; and after being purified, the sulfolane returns to the system, a vacuum tower solvent regeneration unit (B) in the original aromatic extraction system is shut down, and other technical processes and operating parameters are not changed. The industrial plant avoids sulfolane deterioration caused by oxygen infiltration and high temperature regeneration; the pH value of the sulfolane in the extraction system is enhanced from 5.0-6.0 to 6.0-7.0, the chroma is lowered from 6.0 to 2.0, and the chlorine ion content is lowered from 5-7 mg/kg to 1 mg/kg or so; and the industrial plant has the advantages of higher sulfolane quality and lower system operating cost.