Abstract: In the cyanide extraction process of a gold smelting company,the cyanide-containing wastewater is treated through an acidification process to recover copper and cyanide,which are then returned to the cyanide water system for reuse.By optimizing the pH conditions of the acidification process,the copper recovery rate is increased to 98.81 %,while improving the removal rate of thiocyanate ions.Through the development of rapid precipitation technology using calcium chloride,the mass concentration of sulfate ions in the returned cyanide water system is reduced.After application of the optimized acidification process,the mass concentration of sulfate ions in the cyanide water system is reduced by 49.35 %,and the mass concentration of thiocyanate ions is reduced by 16.86 %.This significantly improves the production conditions of the cyanide leaching process,particularly reducing the sulfate ion mass concentration to 23.5 g/L,alleviating the impact of sodium sulfate crystallization on winter production.