Mint water extract containing Cu²⁺ was treated by chitosan chelation-flocculation method, using a single factor experiment, taking Cu²⁺ removal rate as the main indicator. The effects of Cu²⁺ initial concentration, chitosan dosage and pH value on the removal of Cu²⁺ in the removal process of mint water extract were investigated. On this basis, the water extract of mint after reaction was analyzed by UV spectrum, and the precipitates were analyzed by IR spectrum. Results showed that when the initial concentration of Cu²⁺ was 50 mg/L, the amount of chitosan was 1.5mL and the pH value of the system was 8.09 in a weak alkaline environment, the removal of Cu²⁺ in the extract of peppermint was the best, the removal rate of Cu²⁺ reached 76.4%; Ultraviolet spectroscopy showed that the active ingredients in the extract of mint water treated by chitosan chelate-flocculation method retained well and had good removal effect on other ineffective ingredients; Infrared spectroscopy indicated the main functional group to determine the chelating reaction of chitosan is -NH₂ and -OH.