Abstract: During the leaching process of zinc concentrate, chloride ions are continuously enriched in the solution, and the content of chloride ions in the resystem solution is up to 780 mg/L. It is a common problem in hydrometallurgy as how to use efficient, environmentally friendly and low cost dechlorination method. In the study, copper slag was used as dechlorination agent to dechlorinate zinc hydrometallurgy solution. The dechlorination rate of the solution could reach above 76% after small scale test. The dechlorination rate of copper slag could be over 75% when the experimental parameters of dechlorination of copper slag were used in industrial production. As a by-product of zinc hydrometallurgy, the dechlorination technology of copper slag is well used, since copper slag has higher chlorine ion removal rate with no pollution to the environment and low dechlorination cost, and it is safe and reliable that the solution of hydrometallurgical system would not be replaced by impurity ions. The processing cost of the alkaline washing water generated in recycling dechlorinated copper slag is relatively high.