Under the catalysis of ferric chloride and sulfone, o-nitrotoluene was chlorinated at 35-45°C to obtain a chlorinated o-nitrotoluene mixture, and 3-chloro-2-methylnitrobenzene was purified and separated. The product is hydrogenated to give 3-chloro-2-toluidine. Trichloroquinolinic acid is obtained by sulfonation, chlorination, oxidation, and hydrolysis of Surp.