The reduction behavior of free Ag⁺ was analyzed by thermodynamic calculation, and the control technique of Ag inclusions was studied by electrolysis experiments. The results show that the discharge reduction of free Ag⁺ is inevitable. The entrainment of floating anode slime formed by As, Sb and Bi is the key factor for the inclusions of AgCl and Ag colloidal particles in cathode copper. Sb₂O₃ is adopted to purify the copper electrolyte and reduce the floating anode slime, thus effectively inhibiting the inclusions of AgCl and Ag colloidal particles. Under the optimized conditions, the Ag content of cathode copper is reduced to less than 7.5 mg/kg.