NOVELTY - A mixed solution of 2,5-dichlorophenol, xylene and potassium hydroxide solution is subjected to solid-liquid separation, and potassium hydroxide solution and dimethylformamide are added to carboxylation reactor, to obtain carboxylic acid salt stock solution. The carboxylic acid salt stock solution is added to alkylation reactor. A solution of dimethyl sulfate is dripped and the mixture is reacted. The mixture is heated, crystallized, and aqueous layer is subjected to wastewater treatment, and organic layer is processed with xylene and vacuum distilled to obtain dicamba.    USE - Production of dicamba (claimed).    ADVANTAGE - The method enables production of dicamba with high quality and yield by simple, environmentally-friendly and economical method.    DETAILED DESCRIPTION - 2,5-Dichlorophenol and xylene are added to salt reactor, stirred at room temperature and steam heated at 95-105 degrees C. Potassium hydroxide solution is dripped, refluxed, dehydrated for 10-13 hours, to obtain mixed solution of dichlorophenol potassium. The mixed solution of dichlorophenol potassium is subjected to solid-liquid separation, and potassium hydroxide solution and predetermined amount of dimethylformamide as catalyst are added to carboxylation reactor, and replaced with nitrogen. Carbon dioxide is passed to reactor, and pressure is controlled to 1-1.5 MPa. The mixture is stirred and steam temperature is controlled to 70-80 degrees C. The pressure in reactor is maintained at 1-3 MPa and stirred for 14-16 hours. The reaction mixture is sampled and analyzed, and cooled to room temperature, to obtain carboxylic acid salt stock solution. The carboxylic acid salt stock solution is added to alkylation reactor at room temperature. A solution of dimethyl sulfate is dripped for 3-5 hours, and temperature is controlled and the mixture is reacted at 40 degrees C for 7-9 hours. The mixture is sampled and analyzed. Solution of hydrochloric acid is added to mixture, hydrolyzed, and pH value is adjusted to 3. The mixture is heated at 90 degrees C for 1-3 hours, cooled to room temperature, crystallized, pressed in closed filter under nitrogen pressure of 0.1-0.3 MPa and pressure filtered. The cake is dried in drier, automatic packaged, stratified, and aqueous layer is subjected to wastewater treatment, and organic layer is processed with xylene at 100 degrees C and vacuum distilled at -0.085 MPa to obtain dicamba, and xylene is recovered.